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Backflow Tests

To protect the community of Mammoth Lakes’ water supply, the Mammoth Community Water District (MCWD) has a cross-connection control and backflow prevention program in place. The program requires backflow prevention assemblies to be installed and annually tested where cross-connection can occur. The program is mandated by multiple authorities.

What is a backflow prevention assembly? 

Backflow prevention assemblies are devices designed to prevent water from flowing back into the public water delivery system.

Do backflow prevention assemblies need to be tested? 

Yes, backflow prevention assembly testing is required, at minimum, on an annual basis by a certified tester. A list of certified testers can be found below. Costs for testing varies based on many factors. Some testers charge per test, some charge an hourly rate. Each tester/business determines their own pricing. You might expect to see prices in a general range of $85-$200 per assembly (estimate as of March 2023). If your assembly fails or needs repairs, expect additional charges.

Why do I have to install a backflow prevention assembly? 

To protect customers receiving water from the Mammoth Community Water District from potential water contamination.

When is a backflow prevention assembly required? 

Any location where there is actual or potential uncontrolled cross-connections. Common examples of potential cross-connections locations include:

  •      Irrigation systems (residential, commercial and public)
  •      Fire Sprinkler Systems
  •      Swimming pools and spas
  •      Hydronic systems (common example in Mammoth: radiant heating)
  •      Hose Bibs
Other cities do not require backflow prevention assemblies or annual testing for lawn irrigation systems, why does MCWD? 

Due to our mountainous environment (large elevation changes) we have increased chances of backpressure. Furthermore, our water supply is limited to our basin and cannot be imported. MCWD follows the recommendations from the State of California Health and Safety Code. Lawn irrigation systems are considered a high-risk for cross contamination because a backflow incident could introduce fertilizers, pesticides and other lawn chemicals (as well as insects and animal waste) into the community’s drinking water, which could be lethally hazardous.

If I do not use my irrigation system, do I still have to have my device tested? 

MCWD will grant a one year waiver from the testing requirement if the property owner decides not to utilize their irrigation system. If the property owner decides to discontinue use of their irrigation system, they must remove the assembly, cut and cap the irrigation system to be removed from the requirement going forward. An inspection of the removed and capped system is required.


  Backflow Test Report Form:



 Certified Approved Testers:

NameCompany(*local)Phone (t text message ok)EmailTester#
Erik WestfallA&D Plumbing*760-937-0805 taanddplumping@gmail.com11259
Manny BravoBravo Gardens*818-519-0009manny@qnet.com06331
Phil WattsPhil Watts Landscape*760-937-3589 tphiwatts@gmail.com13119
Mike HicksMountain Plumbing*760-709-6818mikeh@mountainplumbing services.com17032
James GrayGrasshopper Inc.*760-382-1975 tjjgray@schat.net16389
Tarek NuttalHighland Plumbing*760-914-9184service@highland-plumbing.com18046
Howard SpezziaA Reliable Plumber*626-252-5836 tarplumber@yahoo.com18070
Matt GraefMatt Graef*760-914-7108 18500
Chanel EgesdahlCommunity Fire Protection775-830-5944 tcegesdahl@community
Jason VolentineJB Fire Systems775-843-3558 17268