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Cross Connection FAQ
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Cross Connection FAQ
| Q.1 |
What is a "cross-connection?" test |
| A. |
A cross-connection is a permanent or temporary connection, which could contaminate your drinking water if a backflow condition occurs. |
| Q.2 |
What is "backflow"? |
| A. |
It's just what it sounds like: the water is flowing in the opposite direction from its normal flow. With the direction of flow reversed, due to a change in pressures, backflow can allow contaminants to enter our drinking water system through cross-connections. Without proper protection devices, something as useful as your garden hose has the potential to poison your home's water supply.
A potentially hazardous cross-connection occurs every time someone uses a garden hose sprayer to apply insecticides or herbicides to their lawn. 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. |
| Q.3 |
How can I prevent a cross connection?" |
| A. |
There are three easy ways you can prevent a cross connection at your home. 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. 3) Use proper protection devices. Each spigot at your home should have a hose-bibb 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. |
| Q.4 |
What is "back-siphonage"? |
| A. |
The flow of unsafe water into a safe water supply caused by a lower pressure in the safe water supply and resulting in contamination. |
| Q.5 |
What is "back pressure"? |
| A. |
"Backpressure" means a pressure (caused by a pump, elevated tank or piping, boiler, or other means) on the consumer's side of the service connection that is greater than the pressure provided by the public water system and which may cause backflow. |
| Q.6 |
What is an air gap? |
| A. |
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 backsiphonage but is not always practical and can easily be bypassed. |
| Q.7 |
What is a reduced principle assembly (RP)? |
| A. |
An RP is 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 backsiphonage and may be used to isolate health or nonhealth hazards. |
| Q.8 |
What is a pressure vacuum breaker assembly (PVB)? |
| A. |
A PVB is 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 nonhealth hazards but is effective against backsiphonage only. |
| Q.9 |
What is a double check valve assembly (DC)? |
| A. |
A DC is 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 backsiphonage but should be used to isolate only nonhealth hazards. |
| Q.10 |
What is a residential dual check valve (RDC)? |
| A. |
A RDC is similar to a DC in that it is a mechanical backflow preventer consisting of 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 than a DC. An rdc is effective against backpressure backflow and backsiphonage but should be used to isolate only nonhealth hazards and is intended for use only in water service connections to single-family homes. |
| Q.11 |
Why do backflow preventers have to be tested periodically? |
| A. |
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 have to be tested with properly calibrated gauge equipment. |
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