Cross-Connection Control & Backflow Prevention

Protecting Our Water Supply

Myoma Dunes Mutual Water Company (MDMWC) works every day to deliver safe, reliable drinking water to our customers. Backflow and cross-connection prevention is an important part of that effort. While our distribution system is designed and maintained to keep water flowing safely from our sources to your tap, hazardous conditions on a customer's property can sometimes put the public water system at risk. MDMWC's Cross-Connection Control Program exists to identify and eliminate those risks before they become a problem.

This program is required under the California State Water Resources Control Board, Division of Drinking Water's Cross-Connection Control Policy Handbook, which requires the installation and annual testing of backflow prevention assemblies whenever a plumbing fixture or system poses a potential cross-connection hazard.

What Is a Cross-Connection?

A cross-connection is any actual or potential physical link between MDMWC's drinking water system and any source of non-potable water, liquid, gas, or other substance. Whenever a plumbing fixture, irrigation system, or piece of equipment is connected to the drinking water supply, a potential cross-connection exists. Common examples include:

• A garden hose submerged in a pool, bucket, or basin of soapy or chemical-treated water
• Irrigation and lawn sprinkler systems without anti-siphon or backflow protection
• Wells, ponds, or other secondary (non-potable) water sources connected to a property's plumbing
• Fire sprinkler systems
• Boilers, chillers, cooling towers, and other industrial or commercial process equipment
• Pools, hot tubs, and water features
• Kitchen sprayers or hoses left submerged in a filled sink

What Is Backflow?

MDMWC's water distribution system is designed to maintain higher pressure than a customer's private plumbing system, which keeps water flowing in the right direction — out to your property, never back into the public main. Backflow occurs when that pressure relationship reverses and water (or whatever it has come into contact with) is pulled or pushed backward into the distribution system. This can happen because of:

• Back-siphonageA sudden drop in system pressure, such as from a water main break, a severed fire hydrant, or high demand during firefighting
• BackpressureA customer's private system (a pump, boiler, or elevated tank, for example) operating at a higher pressure than the public main

If an unprotected cross-connection exists at the moment backflow occurs, contaminants can be drawn into the customer's plumbing and potentially into MDMWC's public water system, putting the safety of the drinking water supply at risk.

Our Backflow Prevention Assembly Program

To guard against these risks, MDMWC requires the installation of an approved backflow prevention assembly (BPA) on services where a potential hazard has been identified, including most commercial, industrial, and irrigation connections, as well as certain residential services (such as those with a well, pool fill line, or other secondary water source). MDMWC maintains an inventory of all backflow prevention assemblies installed throughout our service area and administers a testing and compliance program that includes:

• Annual testing of every BPA in service, performed by a certified backflow prevention assembly tester
• Recordkeeping of assembly type, size, location, and test history for every device in the inventory
• Customer notification when a test is due, and follow-up when a device fails testing or requires repair
• Repair authorization and tracking to ensure failed assemblies are promptly repaired or replaced and retested

MDMWC maintains an inventory of backflow prevention assemblies within its service territory.

Is a Backflow Prevention Assembly Required at My Property?

MDMWC requires a certified backflow prevention assembly on:

• All commercial, industrial, and irrigation water services
• Any residential service with a secondary, non-potable water source on the property (such as a private well, pond, or spring)
• Any property identified during a hazard assessment as posing a potential risk to the public water system

Most single-family residential services are not required to have a dedicated backflow prevention assembly. However, every customer plays a role in protecting the water supply. You can help prevent backflow contamination at home by:

• Never leaving a hose submerged in a pool, bucket, sink, or any container of water
• Using a hose bib vacuum breaker on outdoor spigots
• Confirming that irrigation and sprinkler valves have anti-siphon protection
• Never connecting a hose to a source of chemicals, fertilizers, or pesticides

Testing Requirements & Customer Responsibilities

If MDMWC's records show a backflow prevention assembly is installed at your property, state regulations require that it be tested at least once a year to confirm it is functioning properly. MDMWC will notify you when your annual test is due.

• Testing must be performed by a certified backflow prevention assembly tester
• Test results are recorded and retained in MDMWC's backflow assembly inventory
• If an assembly fails testing, the customer will receive a notice and must have the device repaired or replaced by an authorized technician and retested within the required timeframe

Failure to test or repair a backflow prevention assembly as required may result in enforcement action under MDMWC policy.

Why This Program Matters

Cross-connection incidents are rare, but when they occur they can introduce serious contamination into a drinking water system, potentially affecting not just one property but an entire neighborhood served by the same water main. A functioning backflow prevention assembly is a critical, ongoing line of defense — like any mechanical device, it has moving parts that can wear out over time, which is why annual testing is required even for assemblies that have never failed before.