It is a sewerage vacuum collection system which uses other differential air pressure as well as gravity to rapidly transport sewage in a network of mainly empty pipes from collection puts to a central collection tank and then to a specific area of discharge. A batch of sewage which enters the vacuum system when the atmospheric valve opens in the collection put and the sewage is sucked in the main vacuum. The Flovac valve remains open for sometime following the removal of the sewage coming from the pit sump which allow for atmospheric air to enter into the suction pipe and then blow the sewage batch into the vacuum pump station. Unlike the older type of sewerage systems, the transport in the modern systems is very fast and notable not due on a siphon.
The VPS or Vacuum Pump Station houses a collection tank in order to collect sewage; discharge the pumps to send the sewage in the treatment plant; controls to automate the vacuum pumps and the station which makes a negative pressure in the vacuum mains. Typically only one VPS is being required in an average sized catchment. Ideally, inside the vacuum pump station is located centrally within the catchment area but the designer has to be flexible about this. A back-up generator is typically located at the VPS which ensures non-stop operation in a particular area where power is typically a problem or susceptible to cyclones or hurricanes.
The collection pit houses the 3 inches Flovac Vacuum valve which interfaces in between the atmosphere coming from the gravity lines as well as the negative pressure inside the vacuum mains which are created by the vacuum pumps at the VPS. The VPS can be as far as 3 miles or 5 km away from the last collection pit. When the 40 liters of water enter the pit coming from the gravity line, air pressure coming from the valves controller will trigger the valve to open and will thereby allow the sewage and the air to enter the vacuum at a velocity of 4 to 6 meters every second. It is also expanding air that propels the sewage to the VPS which refers to the point of stronger negative pressure. No power will be required near the collection pit.
The vacuum mains which are either PVC or PE are being designed to be as shallow in the ground and are laid at a 1/500 grade. The contractor then builds steps in the pipework in order to keep the mains from getting very deep. The more steps that will be installed, the more hydraulic losses will be created which lessens the distance that the mains can go.