Vacuum Sewer System Design
Gravity Sewer networks have catchment plans, as do vacuum sewer networks. Ignoring those plans can lead to;
- Excess flows.
- Undersized mains
- Pump stations and treatment plants undersized
- High power use
- Flooding and overflows
- System collapses.
Engineers have a good understanding of the limitations of a gravity system, but how many know about the limitations of the vacuum sewer system? Of course we say that vacuum systems are very flexible. That is true as long as we understand the current state of the system and what is being planned still in the future.
In one recent project the system was performing smoothly and with much lower flows than anticipated, this allowed the engineer to replace two existing gravity pump stations with vacuum pits and take the flow into the vacuum system. A system that is well understood from a planning perspective opens up a lot of opportunities.
Master Plan Information
When we are managing Master Plans for clients and looking at sub division changes we look for the following:
- Are the Master Plans properly updated with as-constructed data.
- What flow rates were originally designed for in the system and what are the current flow rates.
- Have densities changed
- What are the calculated head losses on the vacuum lines
- Is the right emergency storage being allowed for
- Did the original design call for a Pump Station Upgrade at some future population density or flow rate.
- Are there other area’s that could now be accommodated
Operational Knowledge is Key
If we have a good Master Plan in place a request for an extension or sub division can happen fairly quickly. The one area that many designers and approvers forget is in knowing how well the system is currently operating. Our engineers insist on getting a sign off from our operational group prior to an approval.
If the system isn’t coping with the current flow rate then adding a new hotel or group of houses could cause it to collapse. it doesn’t matter what the designs and Master Plans say, if the vacuum valves haven’t been maintained, if infiltration is occurring, if the vacuum pumps need upgrading then you could make the system worse.
Maintaining Master Plans for clients is part of our Asset Management Support program. If you would like more information about this please contact your local Flovac contact.
All systems undergo change during their life time, a group of 4 houses will become 8 or become a 5 story apartment block. A caravan park could become a group of town houses. A school could become a group of apartments. The faster the designer can approve the development the less pressure they will get from a politician or developer. Flovac can help.