Vacuum sewers can be installed more affordably, and cost less to maintain and operate, than gravity systems. Here's how they work:
A traditional gravity line carries wastewater from the customer to a valve pit package.
When 10 gallons of wastewater collects in the sump, the valve opens and differential pressure propels the contents into the vacuum main.
Wastewater travels at 15 to 18 feet/second in the vacuum main, which is laid in a sawtooth pattern to ensure adequate vacuum levels at the end of each line.
Wastewater enters the collection tank; when it fills to a predetermined level, sewage pumps transfer the contents to the treatment plant via a force main.
Vacuum pumps cycle on and off as needed to maintain a constant level of vacuum on the entire collection system.