Backflow Prevention

Backflow is the undesired reversal of water flow between the City’s distribution system and a private system, due to changes in water pressure. This reversal or “backflow” can cause contaminants to enter into the drinking water distribution system such as 

  • Fertilizers and pesticides
  • Human waste
  • Chlorine from pools and spas
  • Soap from sinks, dishwashers, and showers

Causes of Backflow

Backflow can occur due to back pressure or back siphonage.

  • Back pressure occurs when pressure in a private water system is greater than pressure in the City’s water supply system, which may be caused by pumps, elevated tanks, temperature increases in boiler systems, and other local pressure events. This can result in water from the private system forcing its way into the City’s distribution system.

  • Back siphonage occurs when pressure in the City’s water supply system is lower than pressure in a private system, which may be caused by nearby fire-fighting or water main breaks. This reversal of pressure can pull contaminated water from the private water system into the City’s distribution system.

Backflow Prevention

Backflow prevention systems are devices installed onto a pipe that only allow water to flow in one direction. Placed at the site of the cross-connection, they can protect the plumbing system from contamination. Placed just downstream of a water meter to an establishment, they can protect the public water system from contamination that may occur within the entire establishment’s plumbing system.

  • Reduced Pressure (RP) consists of two independently acting, internally loaded check valves, separated by a reduced pressure zone.

  • Double check valve (DC) consists of two check valves, which help to provide protection in the event that one valve does not close tightly. 

Backflow Testing & Repair

To test and repair a backflow device, a person must have a valid Backflow Prevention Assembly Tester Certification through the Iowa Department of Public Health (IDPH).  To verify the status of a backflow prevention assembly tester, visit the IDPH online database, and click on Public Search. Then select Backflow Tester from the Program Name.

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