1. Services for Residents
  2. Power, Water & Sewer
  3. Drinking Water
  4. Cross Connection Control
  5. Cross Connection Protection

Cross Connection Protection

A cross-connection is a permanent or temporary connection, which could contaminate your drinking water if a backflow condition occurs. When you attach a garden hose sprayer to apply insecticides or herbicides to your lawn, there is a risk of contaminating your water source with hazardous chemicals. Without a backflow prevention device between your hose and outside faucet, the contents of the hose and anything it is connected to, can backflow into the water system and contaminate your drinking water. Backflows due to cross-connections are serious plumbing problems; learn more about Cross Connection Control.

Backflow

It's just what it sounds like: the water is flowing in the opposite direction from its normal flow. A change in pressure within the drinking water source can cause a backflow, allowing contaminants to enter our drinking water system through cross-connections. There are two types of backflow: back-siphonage​ (caused by low pressure in the drinking water supply) and back pressure  (when a pump, elevated tank or piping, boiler, or other means on the consumer's side of the service connection has a greater pressure). 

Without proper protection devices, something as useful as your garden hose has the potential to poison your home's water supply.

Prevention

There are three easy ways you can prevent backflow at a cross connection:

  1. Never place the end of a hose where it can suck contaminants into your drinking water,
  2. Leave at least a one-inch gap between the end of a hose and a source of contamination (called an air gap), and
  3. Use a proper backflow protection device. 

​An air gap is a vertical, physical separation between the end of a water supply outlet and the flood-level rim of a receiving vessel. This separation must be at least twice the diameter of the water supply outlet and never less than one inch. An air gap is considered the maximum protection available against backpressure backflow or back-siphonage but is not always practical and can easily be bypassed.

Backflow Prevention Devices

Each spigot on your property should have a hose-bib vacuum breaker installed. This is a simple, inexpensive device that can be purchased at any plumbing or hardware store. Installation is as easy as attaching your garden hose to a spigot. It's important to test all backflow devices annually to ensure they are functioning properly.

Mechanical backflow preventers have internal seals, springs, and moving parts that are subject to fouling, wear, or fatigue. Also, mechanical backflow preventers and air gaps can be bypassed. Therefore, all backflow preventers have to be tested periodically to ensure that they are functioning properly. A visual check of air gaps is sufficient, but mechanical backflow preventers must be tested annually by a licensed backflow tester with properly calibrated gage equipment.

  1. Reduced Principle Assembly (RPA) - A mechanical backflow preventer that consists of two independently acting, spring-loaded check valves with a hydraulically operating, mechanically independent, spring-loaded pressure differential relief valve between the check valves and below the first check valve. It includes shutoff valves at each end of the assembly and is equipped with test cocks. An RP is effective against backpressure backflow and back-siphonage and may be used to isolate health or non health hazards.
  2. Pressure Vacuum Breaker Assembly (PVB)- A mechanical backflow preventer that consists of an independently acting, spring-loaded check valve and an independently acting, spring-loaded, air inlet valve on the discharge side of the check valve. It includes shutoff valves at each end of the assembly and is equipped with test cocks. A PVB may be used to isolate health or non-health hazards but is effective against back-siphonage only.
  3. Double Check Valve Assembly (DC) - A mechanical backflow preventer that consists of two independently acting, spring-loaded check valves. It includes shutoff valves at each end of the assembly and is equipped with test cocks. A DC is effective against backpressure backflow and back-siphonage but should be used to isolate only non-health hazards.
  4. Residential Dual Check Valve (RDC) - A mechanical backflow preventer similar to a double check valve assembly with two independently acting, spring-loaded check valves. However, it usually does not include shutoff valves, may or may not be equipped with test cocks or ports, and is generally less reliable. A residential dual check valve is effective against backpressure backflow and back-siphonage but should be used to isolate only non-health hazards and is intended for use only in water service connections to single-family homes.