pressure sewer

A pressure sewer provides a method of discharging sewage from properties into a conventional gravity sewer or directly to a sewage treatment plant.

Pressure sewers are typically used where properties are located below the level of the nearest gravity sewer or are located on difficult terrain.

Operation

In a typical set-up, a receiving well is provided close to the properties being served so that all sewage can gravitate to the well. An electric macerator pump (also called a grinder pump) pumps the finely macerated sewage through a narrow diameter continuous plastic pipe which discharges into the nearest gravity sewer or treatment plant. The operation of the pump is controlled by a float switch in the pumping well. The pumping well is sized to allow for periods of power outage or pump maintenance.{{cite web|url=https://sswm.info/sswm-university-course/module-2-centralised-and-decentralised-systems-water-and-sanitation/further/pressurised-sewers|title=Pressurised Sewers|access-date=18 January 2022|publisher=Sustainable Sanitation and Water Management Toolbox|author1-last=Stauffer|author1-first=Beat|author2-first=Dorothee|author2-last= Spuhler}}

The discharge pipe may be as small as 50{{Spaces}}mm diameter carrying sewage at very high flow rates. {{Cite web|url=https://www.cedengineering.com/userfiles/LP%20&%20SDGS%20Sewers.pdf|title=Overview of Low Pressure and Small Diameter Gravity Sewers|first=Stephen|last=Huskie|access-date=22 October 2024|publisher=US EPA}}

Pressure sewers are also used to collect the discharge from septic tanks and discharge this into the local gravity sewer to protect local ground water from contamination.{{cite web|publisher=United States Environmental Protection Agency|title=Wastewater Technology Fact Sheet - Sewers, Pressure|url=https://www.epa.gov/sites/default/files/2015-06/documents/presewer.pdf|access-date=18 January 2022|date= September 2002}}

Advantages

Pressure sewers enable properties constructed below the nearest gravity main to connect to the local sewerage system avoiding the need for a septic tank or cesspit.{{cite web|url=https://sswm.info/sswm-university-course/module-2-centralised-and-decentralised-systems-water-and-sanitation/further/pressurised-sewers|access-date=22 October 2024|title=Pressurised Sewers|publisher=Sustainable Sanitation and Water Management University Course|first1= Beat|last1= Stauffer|first2=Dorothee|last2= Spuhler}}

In areas where washouts or earthquakes are common, conventional earthenware or cast iron sewerage system may be prone to breakage and leakage. The plastic discharge pipe of a pressure sewer is much more robust and can accommodate substantial movements in the ground without failing.{{cite web|url=https://aees.org.au/wp-content/uploads/2013/11/Zare-Wilkinson.pdf|title=Wastewater Pipeline Vulnerability to Earthquakes|publisher=University of Aukland|access-date=22 October 2024|first1=M. R.|last1=Zare |first2=S|last2= Wilkinson }}

Costs can be lower than conventional sewers since the pipework is much cheaper and there is no requirement for manholes or other intermediate infrastructure. Installation costs can also be very low as the pipes can be laid very close to the surface and may be installed using no-dig methods such as moleing.

Disadvantages

The pumping well and pump controls require expert maintenance and repair should they fail.

Electricity is required to power the pump and this cost would typically fall on the local house-holder.

Although the pump well is usually designed to accommodate several days storage, failure of the pump or of the local electricity supply for an extended period would result in a local overflow.

References

Category:Hydraulic engineering

Category:Sewerage infrastructure