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Backflow is the reverse flow of water through pipes and hoses. This reverse flow poses a risk of water contamination to public and domestic drinking water systems. For more information please contact the Backflow Team at 208-888-5242.

Information for Residents

  • Back Pressure: Back pressure occurs when the pressure in a pipe or hose is greater than the incoming pressure. Connection to a booster pump or private well. 
  • Back Siphonage: Back Siphonage occurs when there is negative pressure drawing contaminants into the water supply.
  • Cross Connections (Dual Connections): Cross connections occur when two separate water systems are connected together mixing different sources of water (i.e. pressurized irrigation water lines connected to your home's drinking water lines). Through these connections, it is possible to introduce non-potable, used, unclean, contaminated water or other substances into the potable water supply.

  • Back Pressure and Back Siphonage require the installation of an approved backflow assembly to be installed. These assemblies need to be tested annually by a certified backflow assembly tester and the results submitted to the City Water Division. 

Three common types of backflow assemblies can be found here». 

  • Cross Connections (Dual Connections) ARE NOT ALLOWED within the City of Meridian for residential use and must be removed if currently installed. View or download the dual connection removal requirements PDF below.

To find out if you require a backflow assembly, review the process below. 

Do you need your backflow assembly tested quiz

If you need to install a Backflow assembly, a permit is required.  To apply for a permit, visit

As of May 1st, 2018, Double-Check Assemblies are no longer allowed in lawn sprinkler applications.

All backflow requirements will be enforced by the Idaho State Plumbing Code (ISPC). 

Any double-check backflow assemblies installed prior to the code change will not need to be removed unless they can no longer be repaired. At that time, they will need to be upgraded with a Reduced Pressure Backflow Prevention Assembly (RPBP) or a Pressure Vacuum Breaker Assembly (PVB).

City of Meridian Backflow Video


If you have or need a Backflow Assembly it is required it be tested annually. You can find a courtesy list of testers here: 2023 Backflow Tester Pricing Sheet.

Backflow Prevention Assemblies must be tested annually and by a Certified Backflow Prevention Assembly Tester. Test reports must be submitted to the Meridian Water Division on or before their due date to avoid water service interruption.

In order to assist our customers with finding a Certified Backflow Assembly Tester

As a courtesy, the City has created a list of local testers who have volunteered their contact information and pricing. Please select the link below for a copy of the current backflow assembly tester list.

When a backflow prevention assembly is defective or fails to pass the field test, the Backflow Assembly Tester shall submit immediately, if possible, but no later than two (2) business days, a failing field test report to the Meridian Water Division. All repairs must be made within 10 business days and a passing assembly test received by the Meridian Water Division to avoid water service interruption.

City Code: Corss-Connection Control 9.3 »

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