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.

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.

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.

Who are the mandating authorities regarding cross-connection control and backflow prevention?

Code of Federal Regulations, Safe Water Drinking Water Act of 1986
Code of California Regulations Title 17 and Title 22
State of California Health and Safety Code Section 13114.7
California Plumbing Code
California Fire Code
Mammoth Community Water District Water Code, Chapter 12, Division 3, Section 3.34


Cross-Connection Control Specialist
Cecil Bundesen
760-934-2596 x 232 
Click here to email Cecil Bundesen

Backflow Test Report Form:

Backflow Prevention Assembly Test Report – Blank

Certified Approved Testers:

Name Company Phone Email Tester#
Erik Westfall A & D Plumbing 760-937-0805 11259
Manny Bravo Bravo Gardens 818-519-0009 06331
Phil Watts Phil Watts Landscape 760-937-3589 13119
James Gray Grasshopper Inc. 760-382-1975 16389
Jason Volentine JB Fire Systems 775-843-3558 17268
Tarek Nuttal Highland Plumbing 760-914-9184 18046
Howard Spezzia A Reliable Plumber 626-252-5836 18070
Matt Graef Matt Graef 760-914-7108 18500
Mike Hicks Mountain Plumbing 760-709-6818 mikeh@mountainplumbing 17032
Jesse Russell Jesse Russell 775-433-3660 18828
Chanel Egesdahl Community Fire Protection 775-830-5944 18971