Vacuum sewers have few moving parts and require little maintenance. Household wastewater enters through a gravity service line, then empties into a vacuum valve pit, usually located near the street. Two to four homes can be connected to a single valve pit. Each valve pit is equipped with a vacuum interface valve that activates when wastewater in the lower sump reaches a predetermined level, usually about 10 gallons. Valve-pit operation is completely pneumatic, so electrical power is not required.
When the valve activates, wastewater is pulled by vacuum pressure into the collection line, followed by a volume of air. The wastewater forms a slug that is driven by the air due to differential pressure. The slug moves rapidly within the collection main, usually at 15 to 18 feet/second, scouring the pipe and preventing buildup of grease or sludge. And because vacuum technology is a closed system, there are no leaks in the collection main. That means no groundwater infiltration or sewage ex-filtration, reducing treatment costs and protecting groundwater.
Vacuum pressure within the collection mains is created by vacuum stations. A single station can provide service to a very large area, often replacing multiple lift stations that would be required for a gravity-flow system. In Hooper, a gravity-sewer plan would have required about 15 lift stations and hundreds of manholes. By contrast, the vacuum system has only three vacuum stations and no manholes.
Dennis Steele, the construction manager for J-U-B Engineers, estimates the installation cost for the vacuum system was 25% less than a gravity system would have been.Primed For Growth
Hooper's new system, manufactured by Airvac Inc. of Rochester, Ind., recently began operations, and a great deal of attention is focused on how well the technology will work.
“This is the first time vacuum sewer technology has been used in Utah,” says Mayor Glenn Barrow. “We're being watched very closely by the State Department of Water Quality and by other communities. We have beautiful vacuum stations that fit in with the existing architecture, we saved money on installation, and we will continue to save money on maintenance costs.”
Hooper can expect more growth in the coming years. Barrow notes that property values are already increasing, a good sign for Hooper's homeowners and business leaders.
“We want to be smart about our growth, and this new vacuum sewer system certainly looks like a smart idea,” says Barrow.
— Steve Gibbs is a Germantown, Tenn.-based business writer.Related Article
to learn more about how vacuum sewer technology works, click here.