Checking a system capacity with the city engineer

Undersized, or Underperforming? Know Which Before You Invest

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An undersized system and an underperforming one look identical from the control room. They need very different answers — and lessons from power, rail, roads and our own industry show why it pays to know which you have.

Does your sewer system feel undersized — struggling with today’s load, with growth still to come? It is a common conclusion, and sometimes the right one. But before committing capital to a bigger station, a second station or larger vacuum mains, it is worth stopping to ask a harder question: is the system genuinely too small, or is it not performing as it should?

The answer matters, because the two problems look identical from the control room and have very different solutions. An undersized system needs more capacity. An underperforming one needs its existing capacity found and released — usually for a fraction of the cost.

Other infrastructure sectors have learned to tell the difference, sometimes expensively. Their experience is worth borrowing.

Every infrastructure sector has learned this lesson

Power: more from the reactors already running

In October 2026, two of the largest nuclear operators in the United States committed billions of dollars — not to new reactors, but to getting more from the ones they already run. Constellation Energy announced upgrades at 11 reactors across six sites, expected to add 890 MW of capacity, with more than US$4.3 billion invested and the first upgrade online by 2028. Days earlier, the US Department of Energy made a conditional loan commitment of up to US$4.2 billion to Vistra for upgrades at three plants, adding 433 MW and supporting another 20 years of operation.

The industry calls these “uprates”: new turbines, generators and digital controls that let an existing plant safely deliver more. They are major engineering projects, not shortcuts. But they start from a simple discipline — understand precisely how the existing asset performs, find the margin that is genuinely there, and release it before committing to a new facility. Commentators were also careful to note that uprates don’t remove the need for new plants forever. The point is to know which situation you are in.

Wastewater: our own industry learned it fifty years ago

When the US EPA funded municipal treatment works under its construction grants program, applicants had to meet one condition. They had to show that the sewer network feeding a plant was not subject to excessive infiltration and inflow. “Excessive” had a practical, economic definition: extraneous water that would cost less to remove through rehabilitation than to transport and treat. Where the analysis pointed to a problem, a Sewer System Evaluation Survey was carried out to find the sources, their flow rates and the cost of fixing them.

The logic was straightforward. Without that step, communities would have paid to build treatment capacity for groundwater and stormwater. Understanding the network came before sizing the plant. The federal grants program has since been replaced by state revolving funds. The principle has outlived it. Many state programs still ask applicants to demonstrate that their sewers are not subject to excessive infiltration and inflow before treatment works are funded.

The same thinking applies in reverse when a new system is being chosen. At Tea Gardens on the NSW Mid North Coast — a development of close to 3,000 lots on flat, water-charged ground — MidCoast Water selected a Flovac vacuum system partly because of its better wet-weather performance. As the utility’s design manager explained at the time, keeping stormwater and groundwater out of the sewer had a direct payoff. MidCoast Water did not have to enlarge its treatment plant to as large a size as a gravity system would have required. One vacuum station also replaced the 13 pump stations a gravity design would have needed.

Tea Gardens Growth Corridor with a high water table

Tea Gardens high water table area with concerns about infiltration

Whether the asset is a treatment plant or a pump station, the capacity it needs depends on how much water the network lets in.

Rail: one crossover set the capacity of a whole line

For years, London Underground could run only 24 trains an hour on the northern end of the Victoria line, beyond Seven Sisters. The limit was not the trains, the tunnels or the signalling. It was the layout of a single crossover at Walthamstow Central, where trains reverse. Renewing that crossover — alongside the line’s wider signalling and train upgrade — allowed every peak train to run the full length of the line and lifted capacity for stations north of Seven Sisters by more than 40%. The Victoria line now runs 36 trains an hour in the peaks.

The capacity of the system was set by one restriction. Find it, and the rest of the line can do its job.

Roads: same asphalt, better control

On Melbourne’s Monash Freeway, VicRoads trialled a coordinated ramp-metering strategy across six consecutive inbound on-ramps. Compared with the ramp-metering system it replaced, peer-reviewed results showed a significant increase in traffic throughput and reduced travel times — without adding a lane. The approach was then rolled out across 63 on-ramps on the wider upgrade route.

Throughput was limited not by the road itself, but by how traffic was let onto it.

Planning: a hierarchy, not a reflex

Infrastructure Victoria’s 30-year strategy turned the same thinking into a planning sequence. First look at managing demand on existing infrastructure. Next get better use from existing assets. Only then expand existing assets or build new ones. It is a process that applies equally well to a single vacuum pump station.

What this looks like in a vacuum sewer

The question applies to any sewer system. Vacuum systems happen to be one of the easiest places to answer it, because almost everything that matters can be measured.

A vacuum pump station is not simply a set of pumps. Its performance is the product of the whole system: the sewage arriving at each collection pit, the air admitted with every valve cycle, the integrity of the network, the profile of the mains, and the way the station’s controls respond to all of it.

When a station runs long hours, struggles to hold vacuum, or alarms during wet weather, the symptoms show up at the station. The causes are often somewhere else. The ones we see most often include:

  • Leakage. Vacuum pumps evacuate air whether or not sewage is moving. A small leak in a main, fitting or collection pit is a load the station carries 24 hours a day.
  • Valve cycling that doesn’t match the sewage. Valves cycling far more often than the flow from their properties would require, staying open too long, or activating without a genuine sewage load. Each extra cycle admits air the station has to remove.
  • Inflow and infiltration. Rainfall and groundwater entering through property connections, pit lids or damaged gravity laterals, turning a storm into a capacity problem.
  • Network restrictions. Sags, waterlogged sections, poorly configured lifts, or a division valve left partly closed — local restrictions that limit what the whole system can do.
  • Pump condition. Worn vacuum pumps delivering well below their rated capacity, so the station is effectively smaller than its nameplate.
  • Controls and setpoints. Setpoints that have drifted, alarm logic that locks pumps out, or a variable speed drive added to manage a symptom that ends up masking its cause and increasing run hours.

Every one of these makes a system look undersized. None of them is solved by a bigger station. Adding pumps to a leaking network increases energy use and running hours, moves the problem somewhere else, and leaves the community paying for capacity it doesn’t need.

Source: APEX Companies KLWTD Flovac Americas WEFTEC Presentation September 2026

The same applies to the mains. We have had customers consider upsizing their vacuum mains to relieve a struggling system. Replacing buried pipe along an existing route means major civil works, significant cost and real disruption to the community it serves. And where the underlying cause is a local restriction — a sag, a waterlogged section, a poorly configured lift or a partly closed division valve — a larger pipe across the whole route may not address it at all. Finding the restriction first is far cheaper than replacing the network around it.

A system that is underperforming will still underperform after it has been made bigger.

Eight questions to answer before any significant upgrade

Before committing capital to a bigger station, a second station or larger vacuum mains, stop and ask a harder question. Is the system genuinely too small, or is it not performing as it should?

What was the system originally designed to handle? This is usually our first question, and the answer has often been forgotten. Design reports, connection numbers, design flows per person and staging plans can be lost as systems change hands over decades. Many staged designs allowed from the outset for a pump upgrade, or space for a third or fourth pump, as the catchment developed — an option that may already be built into the station.

What is it actually receiving — and if it isn’t performing to design, what changed? Measured flows in dry and wet weather against the original design basis. Design allowances themselves have moved: water use per person has fallen across much of the developed world. In the United States, indoor household water use fell by 22% between 1999 and 2016, largely because of more efficient toilets and washing machines — yet design flows of around 100 gallons per person per day remain common. In Germany, household water use fell from 144 to 126 litres per person per day between 1991 and 2022. In Australia, typical design allowances have fallen from around 230 to around 180 litres per person per day. A system designed on older figures may have more capacity for connections than anyone assumes. If it is struggling below its original design load, the question becomes what changed, and what went wrong.

Water use per person drop

How efficiently is it generating vacuum? Actual pump performance against rated capacity, running hours, and how quickly the station recovers vacuum after load. As a guide, vacuum pumps in a fully developed, well-tuned system typically run around 6–8 hours a day in total, with an air-to-liquid ratio of about 8:1 to 10:1. A ratio approaching 30:1 points to too much air — leaks or tuning. A ratio of 4:1 to 6:1 points to too much water — infiltration, inflow or higher flows than expected.

How are the valves behaving? Cycle frequency at each collection pit against what the connected properties would reasonably produce, and which pits stand out.

Where is air entering that shouldn’t be? Vacuum decay testing, sector by sector: with the vacuum pumps stopped, close the division valves and measure how quickly each section loses vacuum. A tight section holds; a leaking one decays quickly and points to where to look.

Where is the network restricting flow? Line profile, lifts, waterlogging, and valve positions.

Are the controls helping or hindering? Setpoints, pump sequencing, alarm logic and any drives added since commissioning.

What future demand is credible? Committed connections and realistic growth — not a stack of worst-case assumptions.

Only with those answers in hand does it make sense to rank the options. In practice, that ranking usually follows the same hierarchy other sectors use:

Step Response What it means in a vacuum sewer
1 Fix Repair leaks, faulty valves and controllers, damaged collection pits. Cheapest, fastest, and often enough on its own.
2 Tune Correct valve timing, setpoints, sequencing and alarm logic so the existing equipment works as designed.
3 Targeted upgrade Replace worn pumps, relieve a specific network restriction, or improve controls and monitoring where the evidence points.
4 Expand the station Add generating or discharge capacity where measured load and credible growth genuinely exceed what a healthy station can deliver.
5 New station Where the catchment has outgrown what one station and its network can serve hydraulically — a planning decision, not a fault response.

Many stations never need to go past step 2 or 3. Some genuinely do need step 4 or 5 — and when they do, the assessment means the new capacity is sized for the real load rather than for problems that could have been fixed.

Monitoring changes the conversation

Where a system has network and station monitoring, most of these questions can be answered from data that is already being collected: cycle counts for every collection pit, running hours for every pump, vacuum levels through a storm. An upgrade decision becomes a matter of evidence rather than judgement.

Where that data doesn’t exist, a short, targeted monitoring period before design is usually some of the best money a utility can spend. It costs a fraction of a station expansion, and it often changes the answer.

Key Largo, Florida: finding the water before sizing for it

The Key Largo Wastewater Treatment District (KLWTD) serves more than 14,000 people on a low-lying island chain. Its vacuum network spans several stations and is exposed to rainfall, tides and high groundwater. As KLWTD, Apex Companies and Flovac Americas presented at WEFTEC in September 2026, a station can show low vacuum, abnormal demand or slow recovery while the cause sits anywhere upstream in its basin. Traditional troubleshooting narrows the search one isolated section at a time — and wet-weather or tidal conditions have often passed before crews arrive.

Source: APEX Companies KLWTD Flovac Americas WEFTEC Presentation September 2026

With around 2,975 collection pits and buffer tanks monitored, the picture changed:

  • Faster diagnosis. Of 236 system-generated alarms reviewed between October 2024 and May 2026, 147 (62%) were traced to a likely source using location-specific monitoring data.
  • Rain, tide or both. Comparing each pit against its own dry-weather baseline separated rain-driven, tide-driven and combined responses. Some pits were activating more than ten times their normal rate on high-tide days.
  • Targeted field work. In one case, recurring tide-aligned valve activity at a single location led crews to a broken service lateral, confirmed within 48 hours. Field review of the ten highest-ranked screening candidates turned each into an actionable finding — saltwater intrusion at fittings, private-side inflow, a long-standing leak and buffer tank maintenance issues.
  • Scale of the opportunity. A planning-level screening estimate put the excess volume associated with the top 500 candidates at around 20 million gallons for 2025. KLWTD is clear that this is a screening estimate based on an operating approximation per valve activation, not metered or confirmed I&I — but it shows where rehabilitation will release capacity, and in what order.

Every gallon of extraneous water removed is capacity returned to the stations, the transmission mains and the treatment plant.

Source: APEX Companies KLWTD Flovac Americas WEFTEC Presentation September 2026

Exmouth, Western Australia: when the design assumptions changed

Exmouth, on the Ningaloo coast, is served by a Water Corporation vacuum system with a main line of around 2.6 km and a major hotel at its far end. The town’s population of around 2,500 can rise to around 6,000 in peak holiday periods, making inflows extremely variable. The system had also been designed expecting development along the main line that never eventuated — so the air those connections would have added to the main wasn’t there.

During peaks, the line could flood and pressures collapse. With no visibility of pressure beyond the station, operators had to lift pit lids along the line, often at night, and manually open valves to admit air, while wastewater was tankered away until pressures recovered.

In October 2022, Flovac installed pressure monitoring at points along the main and valves that can be opened remotely or by programmed rules. A typical rule works like this. If pressure at one point falls below a set level on two consecutive checks, a nominated valve opens for a few seconds to admit air The system then rechecks. It only acts if the station itself is holding vacuum. Operators can see pressures along the whole line, adjust the rules and setpoints themselves, and activate valves from a screen instead of from the roadside. Rajiv Narendranathan, Principal Engineer at the Water Corporation, presented the work at the AWA conference in Darwin in 2023. He has since noted that the pumper trucks the Water Corporation used to rely on each Easter to keep the system running are no longer needed — a major cost saving for the utility.

This is question two in practice: the system wasn’t too small. What changed was the development pattern it was designed around, and the fix was to restore the air it was missing.

Exmouth Pressure Graph with Automated Air Injection

Flovac monitoring system information page

Sometimes a bigger station is the right answer

This isn’t an argument against investment. Catchments grow. Networks are extended beyond what one station can serve hydraulically. Equipment reaches the end of its life. Resilience and redundancy requirements change. In those situations, more capacity — sometimes a new station — is exactly the right decision.

The aim is simply to know which problem you have: to be confident that the capital is buying genuine capacity, not compensating for leaks, settings or restrictions that could have been resolved for far less.

How Flovac approaches it

Flovac is a specialist manufacturer and supplier of complete vacuum sewer systems, and we support those systems across their whole life — from design assistance and commissioning through to monitoring, optimisation and long-term support. That perspective is why we look at a struggling station as part of a system rather than as a pump problem.

In 2021 we wrote about what to do when vacuum pumps are due for an upgrade We recommended two first steps. A System Audit makes the network airtight and establishes the true air-to-liquid ratio. A Capacity Audit establishes what the system was designed for, and what it can realistically handle over the next 15 years. That advice still stands. Read:My vacuum pumps are due for an upgrade — what next?

We are now combining those two audits into a standard Flovac Capacity and Performance Assessment. We apply it before any significant station or network upgrade. It draws on what we have learned from vacuum systems around the world, combined with the local knowledge that matters most. The operators who run the system every day and usually know exactly where it misbehaves.

Field operator at a vacuum sewer collection pit with a monitoring pillar.

A Flovac operator at a monitoring pillar with a remote mounted controller

If you are planning a change to a vacuum pump station’s pumps, controls or capacity, talk to our engineers early — before the equipment order goes in, not after.

 

DOWNLOAD AS A PDF

Flovac Undersized or Underperforming.pdf

 

 

References

 

 

Flovac operator Jacinta Byrne at the Thargomindah vacuum sewer system during record floods

Built for a Wetter World

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Most sewers were built for a climate that no longer exists. Rain is heavier, seas and groundwater are higher, and storms knock out power more often. This article looks at what that does to sewer networks — and what a network designed for today’s conditions needs to do.

When it rains, it rains harder

A warmer atmosphere holds about 7% more water vapour for every 1 °C of warming. It is basic physics — the Clausius–Clapeyron relationship — and the IPCC’s Sixth Assessment confirms the water cycle is intensifying as a result. When rain falls, it tends to fall harder.

Byron Bay east coast low flooding

Recent events show what that looks like on the ground:

  • Fort Lauderdale, Florida, April 2023: about 25.9 inches (658 mm) of rain in roughly 24 hours.
  • Lismore, NSW, February 2022: the Wilsons River peaked at about 14.4 m, more than 2 m above the 1954 record.
  • Sydney, 2022: 2,530 mm at Observatory Hill, the wettest year in records dating back to 1858.
  • Thargomindah, outback Queensland, 2025: monsoon floods through the Channel Country, hundreds of kilometres from any coast.

For a sewer network, wetter means more intense short downpours, storms carrying more rain, saturated ground, and design storms exceeded more often than their annual exceedance probability suggests. Many existing networks were sized with rainfall data from decades ago. Design guidance such as Australian Rainfall and Runoff has since been updated with larger climate change uplifts — a clear signal that yesterday’s design storms understate today’s loads.

Rising seas lift the groundwater under our towns

Global mean sea level rose about 20 cm between 1901 and 2018, and the rate is accelerating. It averaged about 1.3 mm a year from 1901 to 1971 and about 3.7 mm a year from 2006 to 2018 — nearly three times faster.

This is the part sewer engineers most often underestimate. In coastal areas the water table is hydraulically connected to the sea. Many coastal towns sit on sandy plains where groundwater is shallow and moves with the tide. As the sea rises, the water table rises beneath the whole town, not just at the beach.

A gravity sewer laid decades ago above the water table may now sit in it permanently. Every crack, joint and maintenance hole becomes an entry point, 24 hours a day. Infiltration stops being a storm event and becomes a constant load — and a king tide or storm surge adds more pressure on top.

Rising Sea Levels

Then the storm hits

On a wet day, the effects run down the network in sequence:

  1. Water gets in. Groundwater seeps through cracked pipes, displaced joints and private property sewers. Stormwater enters through illegal downpipe connections and over flooded maintenance hole lids.
  2. Pumping stations are overwhelmed. They are often at low points, so they are also the first assets to flood or lose power.
  3. Treatment plants are overloaded. A surge of diluted wastewater reduces treatment performance and can upset biological processes.
  4. Untreated sewage overflows. It ends up in rivers, bays and on beaches, or surcharges back into homes and yards.

Every litre of groundwater in the pipe takes capacity away from the sewage the system was built to carry. It also costs energy at every pumping station it passes through, and it drives capital upgrades that are really just paying to handle clean water.

Most utilities know they have an infiltration problem. Few know exactly where it is. Flow monitoring shows how much water a catchment takes in, not which pipe or property. Smoke testing finds inflow connections but misses groundwater seepage. And private property sewers — often the biggest contributor — are rarely inspected. So rehabilitation budgets get spread across whole catchments, and groundwater finds the next weakest joint.

Built for a wetter world

If you were designing a sewer network from scratch for these conditions, you would want it sealed against groundwater, able to keep working in a flood, built with few critical assets, easy to back up with standby power, and able to tell you where water is getting in. Vacuum sewerage is not new — it has decades of service history around the world — but its characteristics match that brief closely.

In a vacuum system, wastewater flows by gravity from the home to a nearby collection pit. When the sump fills, a vacuum interface valve opens and draws the wastewater into small, shallow mains, typically 1–1.5 m deep. A single vacuum pump station keeps the network under vacuum and sends flow on to treatment.

A sealed network. The mains are sealed, pressure-tested pipework with no maintenance holes, and the collection pits are sealed chambers. Because the whole network runs under vacuum, a breach shows up at the station as vacuum loss or longer pump run times. Infiltration stops being a slow, silent cost and becomes an alarm.

One station, not many. In flat terrain a gravity sewer keeps getting deeper to hold its grade, so it needs pumping stations to lift it back up. A vacuum system covering the same area can often be served by a single station. That means fewer assets to maintain, flood-proof and keep powered. The exact ratio depends on topography and density.

One power point. Storms take out the grid when the sewer is needed most — at the peak of ex-Cyclone Alfred in March 2025, more than 300,000 homes and businesses in south-east Queensland lost power. A permanent standby generator at every pumping station is rarely affordable. At a single vacuum station, built above flood level, it is standard practice.

No electrics in the street. Vacuum valves are opened by the vacuum itself, so there is no electricity at the collection pit. The Australian standard AS 4310 requires the valve, controller and fittings to keep operating while immersed to 1.5 m. Flovac’s valve and controller have been independently tested by DEKRA to ensure it meets the flood standards around the world. When the floodwater goes down, there is nothing electrical in the street to dry out or replace.

Shallow to build. Small mains in shallow trenches mean far less deep excavation and dewatering in coastal sands with a high water table.

A vacuum pump station is the only piece of infrastructure requiring electricity within the vacuum sewer system.

Vacuum Pump Station, this single station manages nearly 3,000 dwellings on flat land and is the only place where electricity is required.

Monitoring shows where the water gets in

With valve monitoring, every opening of every vacuum valve is logged and time-stamped. A normal household has a recognisable rhythm: busy mornings and evenings, quiet nights. A valve cycling several times an hour at 3 am in the rain is telling you water is entering at or near that property.

Key Largo, in the Florida Keys, shows how this works in practice. The Key Largo Wastewater Treatment District (KLWTD) operates a vacuum system serving low-lying canal homes with high groundwater, big tides and frequent storms. Flovac Americas refurbished the system’s valves and installed its monitoring.

Comparing valve activations at three monitored pits against each pit’s own dry-day baseline, each one responded to something different:

Pit High tide Rain Rain + high tide What it tells the crew
Pit A 1.1× 2.0× 2.3× Responds to rain, barely to tide: rain-driven ingress
Pit B 10.2× 2.3× 1.5× Ten times busier at high tide: tide-driven groundwater
Pit C 5.8× 1.1× 10.3× Worst when rain meets high tide

Activations relative to each pit’s dry-day baseline (1.0×). Data: KLWTD, Apex Companies and Flovac Americas, presented at WEFTEC 2026.

At one pit, D4, valve activations tracked the tide so closely in October 2022 (a correlation of 0.73) that crews went straight to the property and found a broken service lateral within 48 hours. No catchment-wide survey was needed — just one address.

The data tells the operator where to look; the crew confirms the cause. Occasionally that turns out to be a valve or controller needing attention rather than ingress. Either way, the search narrows from a catchment to a pit.

A monitoring system can link in tidal information and rainwater information to detect infilration and inflow

Locating tidal infiltration via monitoring

 

Where vacuum fits — and where it doesn’t

Vacuum is not the answer everywhere. It is strongest in:

  • flat or gently undulating terrain
  • high groundwater, flood-prone and coastal areas
  • rock or difficult ground
  • environmentally sensitive sites
  • low-to-medium density, new estates and septic replacement.

It needs thougtful design: there are some practical limits on total lift, the station must be sited above flood level with odour control, and operators need a valve maintenance regime and training. In very steep terrain, gravity or pressure sewers may be the better choice.

The places where vacuum is strongest are the same places east coast lows, cyclones, hurricanes and floods are hitting hardest — from the Florida coast to the Central Coast, and outback towns like Thargomindah.

Built for the world we have now

Many networks were designed for conditions that have since changed. A network for today should be sealed, flood-resilient, have few critical assets and resilient power, and tell its operators where water is getting in.

Flovac is a specialist manufacturer and supplier of complete vacuum sewer systems. We work with local engineers, utilities and operators from design through commissioning, monitoring and long-term support — bringing experience from projects around the world to each site’s own conditions.

Vacuum systems can still operate when your suburb is completely flooded

Kurnell under water but still operating

Thinking about a catchment with high groundwater or a history of wet weather overflows? Talk to us about a site-specific comparison of gravity and vacuum, worked through with your engineers.

Sources

 

  • IPCC AR6 Working Group I (2021): water vapour per °C, sea-level rise 1901–2018 and rates of rise
  • CSIRO and Bureau of Meteorology, State of the Climate: Australian rainfall extremes and regional sea-level rise
  • NOAA National Weather Service: Fort Lauderdale rainfall, April 2023
  • Bureau of Meteorology: Lismore 2022 flood peak; Sydney 2022 annual rainfall
  • Energex outage reporting, 8–9 March 2025: ex-Cyclone Alfred
  • Australian Rainfall and Runoff (Geoscience Australia): climate change guidance
  • AS 4310 and EN 16932-3:2018; DEKRA test report (flovac.com)
  • KLWTD, Apex Companies and Flovac Americas, WEFTEC 2026: Key Largo monitoring data

Links

Miles Crossing USA 

Apalachicola, USA

Key Largo USA

Thargomindah Australia

Central Coast Australia

DOWNLOAD AS A PDF

Flovac Built for a Wetter World.pdf

The carbon footprint of sewer technology choices Flovac

The carbon footprint of sewer technology choices

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The carbon footprint of sewer technology choices — and why it matters more than most options studies suggest

June 2026  ·  Based on confirmed operational data from Fishermans Bay, South Australia  ·  6 min read

When engineers compare vacuum, gravity, and low pressure sewerage in an options assessment, the comparison is almost always financial. Capital cost. Annual operating cost. Thirty-year NPV. These are legitimate measures, but they capture only part of the picture. The carbon performance of each technology — across construction, materials, operation, and end of life — is rarely quantified, and on certain classes of site it differs by an order of magnitude.

Flovac has published a detailed carbon footprint comparison using confirmed data from the Fishermans Bay vacuum sewer system in South Australia, a 400-dwelling coastal community commissioned in 2022 and monitored continuously by the Flovac FMS platform. The findings are relevant to any engineer working on flat, low-lying, or high water table sites — which describes a significant proportion of Australian and New Zealand coastal and peri-urban development.

6.5×
More energy used by grinder pumps vs vacuum — same site, confirmed data
48,000
Grinder pump mechanisms over 50 years at 12,000-home Riverlea SA
14:1
Gravity pump stations avoided at Prestons Park NZ — confirmed by Aurecon

 

The energy comparison is stark — and mostly invisible

Vacuum energy consumption at Fishermans Bay is confirmed from SCADA data: 7,396 kWh per year for the entire 400-dwelling scheme. A low pressure grinder pump system for the same site would consume approximately 48,000 kWh per year — 6.5 times higher. But that energy does not appear in the utility’s electricity bill. It is distributed across 400 private accounts, each paying approximately $48 per year in additional energy costs to run their grinder pump. The carbon is real. It simply does not show up unless someone specifically looks for it.

Construction carbon — the category nobody counts

On a flat coastal site like Fishermans Bay, gravity sewerage would require trench depths of 3 to 4 metres to achieve fall, with active groundwater dewatering for the full construction duration. The vacuum system was installed at 1.5 metre depth with no dewatering required — documented in the construction contract. Dewatering for a gravity single-station scheme on this site would consume an estimated 144,000 kWh during construction alone — nearly 20 times the vacuum system’s annual operational energy — generating approximately 39 tonnes of CO₂e before a single pipe is laid.

That construction carbon does not appear in any standard options assessment. It is treated as a contractor cost and excluded from the technology comparison entirely.

The wet weather multiplier gravity carries — and vacuum doesn’t

The SA CWMS Design Criteria (LGA SA / Dept Health and Wellbeing, 2019) requires gravity systems in coastal holiday communities to be designed for a hydraulic load 1.5 times the standard peaking factor applied to average daily flow — specifically to account for wet weather infiltration and inflow. Vacuum and low pressure systems are not subject to this multiplier.

This means gravity pipes, wet wells, and pump stations on sites like Fishermans Bay must be physically larger than actual sewage generation requires. That additional material — concrete, pipe, steel — carries embodied carbon that exists solely to accommodate water that should not be in the sewer system at all. And the treatment plant must be sized for a peak wet weather flow that may include groundwater and, on tidal sites, saline water — processed at the full energy and carbon cost of treatment.

The embodied carbon of grinder pump replacement

Grinder pump mechanisms require replacement approximately every 10 years — confirmed by major utilities including JEA in Jacksonville, Watercare in Auckland, and Victorian water corporations. Over a 50-year study life, a 400-dwelling LP scheme requires the manufacture and disposal of 2,000 pump mechanisms. A 12,000-dwelling development like Riverlea in South Australia — a flood plain site with standing water at 2 metres — would require 48,000 mechanisms over the same period. Vacuum collection chambers have a 50-year design life and are manufactured from recyclable polyethylene. There is no equivalent replacement cycle.

How the numbers scale

“The 203-hectare Prestons development would have required approximately 14 traditional wastewater pump stations. The whole site can be serviced by one vacuum pump station. You also don’t have to dewater the ground to lay the pipes.” — Alistair Greig, Project Director, Aurecon (Infrastructure News NZ, November 2013)

Project Dwellings Vacuum pits LP mechanisms (50yr) Gravity stations avoided
Fishermans Bay SA 400 101 (once) 1,600 3 wet wells
Calypso Bay QLD 2,600 650 (once) 13,000 20 wet wells
Prestons Park NZ 2,200 500 (once) 11,000 14 (confirmed)
Riverlea SA 12,000 3,000 (once) 48,000 35–40 wet wells

What this means for engineers

A standard options assessment that compares capital cost and annual operating cost is not wrong — it is incomplete. It excludes construction phase carbon, fails to count distributed LP energy, does not account for grinder pump replacement embodied carbon, treats the wet weather design load as a hydraulic constraint rather than a carbon variable, and excludes end-of-life recyclability. On flat, coastal, or high water table sites, correcting these omissions consistently strengthens the relative carbon position of vacuum sewerage.

The full carbon footprint comparison paper — including methodology, confirmed data from Fishermans Bay, and indicative figures for all four technologies across a 50-year study life — is available for download below.

Download the full technical paper — Carbon Footprint Comparison:
Vacuum, Gravity and Low Pressure Sewer Systems

DOWNLOAD THE PDF

Botswana Delegation Conducts Successful FAT Tour in Europe

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In June, a delegation of 10 representatives from Botswana travelled to Germany and The Netherlands to conduct a Factory Acceptance Test (FAT) for various components of the Vacuum Station.

The group included members from the Government of Botswana’s Department of Technical Services, Water Utilities Corporation, the consulting engineering firm Bothakga Burrow, the environmental consulting firm, and the construction company, Ossy & Classic Clean JV. Andrew Davies from Multi Waste (Flovac’s licensee in Botswana) and Wouter Harperink from Flovac Germany also joined the tour.

Group Picture in front of the Flovac Office

 

The trip began in the picturesque town of Herborn, Germany, with a visit to the Herborner Pumpenfabrik. There, the group was welcomed by Managing Director Wolfram Kuhn—great-great-grandson of the company’s founder—who guided them through the production process of Herborner’s sewage pumps. The FAT was successfully completed on the testing rig, demonstrating the pump’s capabilities.

FAT test of the Herborner sewage pump

 

Inside the Flovac Vacuum Station of Dolgen

On the second day, the team visited a Flovac vacuum system in Dolgen, Germany. The Director of Operations, together with local maintenance personnel from Stadtwerke Sehnde, explained the functionality and operation of the vacuum system. Later that afternoon, the group toured Beisner Elektrotechnik, a family-owned company with extensive experience in manufacturing electrical cabinets for Flovac and for this particular project.

 

 

 

 

 

 

 

 

 

Botswana consultant meets welder of a vacuum tank

The third day featured a visit to the production facility of A. Leering Enschede in The Netherlands, where the FAT of the stainless-steel vacuum tank took place.

Known for delivering top-quality stainless-steel components for high-end clients, Erik Vunderink walked the team through each step of the production and quality control process. A highlight of the visit was a meeting between the Botswana consultant and the welder responsible for constructing the vacuum tank.

 

 

 

 

 

 

In the afternoon, the group visited Flovac’s main production facility, where they observed the manufacturing and testing processes of the vacuum valves, controllers, and monitoring system. On the in-house testing vacuum system, the full functionality of the components was demonstrated.

Testing Controllers at Flovac

 

 

On the final day of the tour, the group visited Busch Vacuum Solutions in Woerden, where they learned about the advantages of the Mink rotary claw vacuum pump. The visit concluded with a guided tour of the facility, followed by a relaxing boat tour through Amsterdam’s iconic canals.

Testing of Vacuum Pump at Busch

 

Canal Tour of Amsterdam

Flovac would like to express its sincere appreciation to the representatives from Botswana for their time, cooperation, and the successful completion of the FAT. We also extend our gratitude to all our suppliers for their hospitality, dedication, and ongoing partnership. We look forward to continued collaboration for many years to come.

Resilience in Action: How Vacuum Sewers Protected a Flooded Town

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How Vacuum Sewer Systems Helped Thargomindah Survive Australia’s Record Flood

In April 2025, the remote outback town of Thargomindah, Queensland was struck by the worst flooding in its history. Entire paddocks turned into inland seas. Emergency shelters filled. And yet, despite the odds, the town’s vacuum sewerage system held its ground — quite literally — thanks to smart planning, fast logistics, and the heroic commitment of one family and their monitoring system.

The Flood That Changed Everything

Thargomindah Flooding

The Bulloo River spilled over in March and April, inundating homes, council infrastructure, and even the camping ground where many residents sought temporary shelter. Despite this, toilets kept flushing, and ablution blocks stayed online — a quiet miracle powered by vacuum technology and dedication on the ground.

To add perspective. The flooded area was the size of Vistoia or three times the size of The Netherlands

 

 

 

What the Council Did Right (Before the Rain)

Jacinta Byrne Hometown Hero

 

 

The Bulloo Shire Council, together with Flovac, had already begun preparations the year before. Actions taken included:
• Raising controller pillars above flood levels.
• Stocking spares in advance and securing supply lines.
• Using real-time monitoring to identify problems before they escalated.

 

 

 

 

 

Even though floodwaters exceeded predicted levels and entered pits and controller enclosures, the raised design made recovery and cleaning easier.

 

 

Cleaning Up still had to take place

 

When Monitoring Saves the Day

Between March 25–29, vacuum pressures in the system plummeted and valve activations surged to over 800 per day, causing alarms to light up across the system. But this wasn’t failure—it was stress detection.
Flovac’s wireless monitoring allowed local technician Daryl Byrne to track the situation in real time, identify failing pits, and respond before services broke down.

Wireless Monitoring System

 

 

Even in such a remote location the wireless system could still function

 

 

The Byrne Family: Unsung Heroes of the Outback

With Daryl’s help, Jacinta and Dalton Byrne were out in the field daily—and nightly. According to Daryl:

The Byrne family,  jacinta and Dalton On call 24 hours

“There were some late nights and early mornings when Jacinta would come and grab Dalton at 3 a.m., saying we’ve got a red light. They’d both head out and by morning have all green lights, just in time for everyone needing the toilets.”

They manually cycled pump stations to ensure flow from flooded ablution blocks, restored failed pits, and cleaned and tested each unit before handing them back to Council.

Why Vacuum Systems Are Built for Resilience

  • Are sealed and airtight, preventing stormwater infiltration into the vacuum network.
  • Areas where infiltration was occurring from homes was easily identifiable.
  • Allow for elevated control installations.
  • Operate with centralised pump control, avoiding multiple flooded pump stations.
  • Can be remotely monitored and manually overridden during emergencies.

Flovac Support in the Background

Even during regional isolation, Flovac delivered new parts to Thargomindah in days. Their stock network and manufacturing readiness meant that vital equipment was replaced quickly, preventing service interruptions.
Lessons for Other Councils
1. Elevate infrastructure where you can.
2. Monitor and maintain in real time.
3. Train local champions—they make or break emergency response.
4. Choose vacuum when terrain and weather challenge gravity systems.
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Closing
In the end, this wasn’t just a test of pipes and valves—it was a test of people and planning. Thargomindah passed.

Proud dad Daryl with Jacinta. Dalton out helping, not in picture. he said he was too busy working.

Retirement of Founding Partner Willem Gooren

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Flovac’s global management team gathered in Greece to congratulate Mr Willem Gooren on his retirement from the business he co-founded in 2005.

Mr Gooren has been involved with vacuum technology since 1981 and established Gooren BV in Holland in 1988. Mr Gooren has designed over 200 systems and has established 15 Flovac offices throughout Europe, the Middle East and Latin America. Mr Gooren is widely considered one of the experts in vacuum technology and was a member of the European committee that developed the first vacuum sewerage standard in the world, EN 1091, the European standard that is now used throughout the Middle East and Asia as well as in Europe.

Willem will still be involved in some ongoing projects in the Middle East as there are very few people with his years of expertise that can assist in some of the more challenging projects that are found there.

We all wish Willem and his wife Rosa and family all of our best wishes and our hearfelt thanks for all of his guidance over the years.

How to identify 5,000,000 litres per year of salt water entering your sewer network at a single glance

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For many coastal communities, infiltration from stormwater and inflow from ground water (I&I) causes major problems. Not only are systems not designed to handle large extra flows, but the additional power costs and operational problems can bring a network to its knees.

St Huberts Island

The coastal community of St Huberts on the central coast of New South Wales in Australia is a beautiful town, surrounded by fantastic fishing spots and has a very high water table. As is common in these coastal communities a vacuum sewer system has been installed to handle the wastewater from the houses. The system was installed in the mid nineties and over the years there has been an increase of I&I into the system.

Vacuum systems are usually installed in high water table areas because they are less susceptible to infiltration than are gravity systems. Over time homeowners gravity pipes and even old collection pits can break and allow ground water to enter the system.

Central Coast council realised that they had a problem which left their residents vulnerable to a loss of service and hire Flovac to come up with a solution that would help locate areas within the network where stormwater was entering the network.

Flovacs monitoring system was installed and within weeks it became evident that the system was taking in water, not only during storm events, but also during high tides. Vacuum valves within the vacuum collection network operate pneumatically every time 40 litres of water enters the collection sump. In this community we would expect to see each valve operating 40-50 times per day or 2,000 litres. In the first month we noticed that one pit was activating between 200 and 500 times per day, even when it wasn’t raining. When it rained it activated even more. this represented between 10-17,000 litres of water every day.

The collection pits in most of this community were old and made out of fibreglass. Over the years there was some evidence of wear. when operators investigated this particular pit, highlighted by the monitoring system, they found that the floor of the pit was broken, allowing ground water to enter the sump. once discovered, the pit was replaced and you can see that from mid August the daily valve activations have reduced to only 10 activations per day as it was found that one of the houses connected was empty.

You can see from the video that water is entering the sump from the pit bottom and not from the incoming gravity line. As this is a high water table area, it was discovered that all of this water was salt water from the bay. each year this pit was adding at least 5 million litres of sea water to the system. A program is now in place to locate other points of infiltration.

The operators having had great success with this, also installed monitoring at a nearby town. After the first major storm, more than 20 collection pits had more than 300 activations each, a major amount of infiltration.

Without Flovacs monitoring system it would of been impossible to locate the problem

Contact Flovac to find out how we can solve your I&I problems.

First Vacuum System in the French Caribbean

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Flovac has recently commissioned the first vacuum sewer system in Grand Case in the French Caribbean. Other systems have already been installed by Flovac in Saint Vincent and the Grenadines, Puerto Rico and the Netherland Antilles.

Grand Case is a small tourist town on the French side of the island of Saint-Martin, with a long beach with turquoise waters. It is well known for the large number of bars and restaurants located next to the beach and along its main street.

Flat and sandy terrain with a high-water table

With such a high-water table a conventional gravity sewer would have been too difficult and expensive to install and would have required multiple pump stations. Fortunately, by installing vacuum mains, all pipework could be laid between 1.2-1.8 meters (4-6 feet) deep and above the water level.

Another advantage of installing vacuum mains is the absence of ground water infiltration into the network. This is very hard to prevent in gravity networks when the pipes are laid under the sea level. When gravity pipes take in ground water it causes problems at the treatment plant. Not just through increased flows but also through the salinity of the water.

Just as you don’t get infiltration, it is also impossible to get exfiltration. The negative pressure in the vacuum mains shows sewage cannot leak out. (shown here)

The leak tightness test is done daily throughout the pipe installation. As Grand Case is an important tourism area, it relies on fresh seafood for its restaurant area and clean beaches.

A single pump station

Only one vacuum station is required to service the entire area, even with its very busy bar and restaurant area. A stainless steel collection tank collects the sewage and a generator os provided to ensure continual power supply to the vacuum pumps and sewage pumps. The area is at risk from major storms and hurricanes and was devasted in 2017 from Hurricane Irma, so power at only a single location can keep the systems running. See more about the hurricane impact here

Please contact us for more information

Why is a Vacuum Sewer the Best Collection System for the Environment

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Gravity/Low-Pressure/Vacuum – which has the Greenest Credentials

It is very clear that septic tanks and cesspools are a disaster for the environment for a number of reasons. Leaking into waterways, poisoning fish and water birds, creating algae blooms. Affecting the overall health of the community.

The choice of a gravity sewer, low pressure sewer (grinder pump) or vacuum system is not as clear in many peoples minds. In many communities the health of the

Clean waterways are essential

community is important, but even more so, the health of the environment. Many people move to coastal communities because of their love of the natural environment. Maybe the beautiful lake, their favorite beach or special fishing spot. If the area is being affected by sewage spills or sewage smells on a regular basis, closing beaches or impacting local shellfish, how will that affect their property prices and quality of life.

Naturally, the cost of sewerage infrastructure is a critical factor, lets take that as a given, if costs are close to equal, what type of system would be best for the environment?

When clients have done carbon footprint studies in the past, the main areas they look at are in construction, materials and whole of life operational costs which include product replacements and energy use.

Construction

Gravity sewers tend to be either laid deep in the ground or have multiple pump stations. Deep sewers can mean pipes laid at 5-10 metres (15-30 feet deep trenches), we have seen deeper. In coastal areas this can mean dewatering which can impact the water table. If a contractor is dewatering the trench, that water goes somewhere else. This can impact the overall watertable which can kill off vegetation or impact the aquifer. Whole eco systems can be affected.

Both vacuum and low pressure systems tend to have shallow pipework and construction time is short. That means that equipment at site is much shorter. A project might be installed in a matter of months rather than years. A major carbon impact.

 

Construction Environmental Impact

Materials

Coastal area’s gravity sewers need either large diameter pipes or multiple pump stations. One of our earlier costal communities we used one vacuum pump station to replace 17 gravity pump stations. The amount of equipment required in 17 stations would be tremendous.

Low pressure systems it’s even worse. In a community of 1,000 houses, you would need 1,000 pumps and pump chambers. In a vacuum system you would require only 200-250 chambers. Vacuum collection pits are not filled with metal pumps and electrical components. They house vacuum valves which have a 50-year design life with minor parts changes every 10 years. The valves bodies from Flovac have a recycle stamp on them as the PP and GP can be recycled.

Whole of Life Operational Costs

Energy costs are the largest component of operational costs in sewer systems.

In cases such as the one in the section above where one vacuum pump station replaced 17 gravity stations, you can be sure that the energy costs of 17 stations were a lot more than a single vacuum station. That system looked after 1,800 houses. A low pressure pump system would require 1,800 pumps, each one requiring electricity.

Due to the low energy requirements, some vacuum systems are now being powered by solar.

The Bigger Risks

Sewerage leaking into the waterways.

In gravity sewers, you could have leaks for months before someone reports a bad smell or something nasty floating in the lake.

Low pressure sewers use a positive pressure and if there is a pipe break sewage can be squirt meters into the air and can be very hard to contain. Contamination of waterways can occur quickly.

Vacuum sewers cannot leak. They operate under a negative pressure and in some projects you will see water and vacuum sewer pipes in the same trench as you cannot get sewage leaking out of the pipe. This video shows how that is possible.

Other benefits

When we installed the vacuum system at the Eco Resort Couran Cove south of the Great Barrier Reef in Australia there were a number of reasons why a vacuum sewer was chosen – You can read about the project here. 

The environmental benefits that they looked at were:

  • Ability to handle low flush toilets thus reducing the ultimate treated water disposal problem
  • Minimal impact on the landscape during construction with shallow trenches
  • Maximum water recovery for reuse in the re-vegetation irrigation system
  • Construction route flexibility thus minimizing the damage to vegetation
  • Ability to transport grey and black water in the one small bore pipe
  • Ability to safely lay all services in the one trench with minimal spacing
  • Zero infiltration and exfiltration
  • Ability of the system to service the entire site with one centralized pump station
  • Ability of the scheme to service the Boardwalk accommodation and even the boat sullage

Flovac vacuum systems are referenced as The Green Future of Sewerage. It is easy to see why. What outcome do you want for your community, lets hope its the Green one.