Licensed Plumbing Contractor CFC1429321
Fire Protection System Contractor V FPC 15-000102


What is cross-connection?

Any actual or potential connection between a drinking water supply and a possible source of contamination or pollution (eg, a wastewater line).

What is backflow?

Backflow is the undesirable reversal of flow of nonpotable water or other substances through a cross-connection and into the public water system (potable water). There are two types of backflow – backpressure and backsiphonage. A backflow system is designed to protect the potable water from contamination, which could occur if the pressure exceeds potable water pressure over a cross-connection where one (or more) of the check valves fail.

What is a backflow preventer?

A backflow preventer is a means or mechanism to prevent backflow. The basic means of preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier to backflow. The basic mechanism for preventing backflow is a mechanical backflow preventer, which provides a physical barrier to backflow. The principal types of mechanical backflow preventer are the reduced-pressure principle assembly, the pressure vacuum breaker assembly, and the double check valve assembly. A secondary type of mechanical backflow preventer is the residential dual check valve.

Why should I test these devices every year?

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.

What is backpressure backflow?

Backpressure is backflow caused by a downstream pressure that is greater than the upstream or supply pressure in a public water system or consumer’s potable water system. Backpressure (i.e., downstream pressure that is greater than the potable water supply pressure) can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both. Increases in downstream pressure can be created by pumps, temperature increases in boilers, etc. Reductions in potable water supply pressure occur whenever the amount of water being used exceeds the amount of water being supplied, such as during water line flushing, fire fighting, or breaks in water mains.

What is backsiphonage?

Backsiphonage is backflow caused by a negative pressure (i.e., a vacuum or partial vacuum) in a public water system or consumer’s potable water system. The effect is similar to drinking water through a straw. Backsiphonage can occur when there is a stoppage of water supply due to nearby fire fighting, a break in a water main, etc.