Cross-connection Frequently Asked Questions

• What is a cross-connection?
• What is backflow?
• What is backpressure backflow?
• What is backsiphonage?
• Why do water suppliers need to control cross-connections and protect their public water systems against backflow?
• What is a backflow preventer?
• What is an air gap?
• What is a reduced principle (RP) assembly?
• What is a pressure vacuum breaker (PVB) assembly?
• What is a double check valve assembly?
• Why do backflow preventers have to be tested periodically?
• What are the City of Salem's requirements for backflow testing?
• How do I know when my device needs to be checked?
• Who are the certified backflow prevention device testers for the Salem area?

What is a cross-connection?

A cross-connection is any temporary or permanent connection between a public water system or consumer's potable (i.e., drinking) water system and any source or system containing non-potable water or other substances. An example is the piping between a public water system or consumer's potable water system and an auxiliary water system, cooling system, or irrigation system. Top

What is backflow?

Backflow is the undesirable reversal of flow of nonpotable water or other substance through a cross-connection and into the pipe of a public water system or consumer's potable water system. There are two types of backflow... backpressure backflow and backsiphonage. Top

What is backpressure backflow?

Backpressure backflow 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 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 boiler, 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. Top

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 through a straw. Top

Why do water suppliers need to control cross-connections and protect their public water systems against backflow?

Water suppliers usually do not have the authority or capability to repeatedly inspect every customer's premises for cross-connections and backflow protection. Alternatively, each water supplier should ensure that a proper backflow preventer is installed and maintained at the water service connection to each system or premises that poses a significant hazard to the public water system. Generally, this would include the water service connection to each dedicated fire protection system or irrigation piping system and the water service connection to each of the following types of premises: (1) premises with an auxiliary or reclaimed water system: (2) industrial, medical, laboratory, marine or other facilities where objectionable substances are handled in a way that could cause pollution or contamination of the public water system. Each water supplier should also ensure that a proper backflow preventer is installed and maintained at each water loading station owned or operated by the water supplier. Top

What is a backflow preventer?

A backflow preventer is a means of mechanism to prevent backflow. The basic means of preventing backflow is an air gap, which either eliminated 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 preventers 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. Top

What is an air gap?

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 be easily bypassed. Top

What is a reduced principle (RP) assembly?

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 non-health hazards. Top

What is a pressure vacuum breaker (PVB) assembly?

A PVB assembly is a mechanical 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 backsiphonage only. Top

What is a double check valve assembly?

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 non- health hazards. Top

Why do backflow preventers have to be tested periodically?

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 equipment. Top

What are the City of Salem's requirements for backflow testing?

As required by Oregon Administrative Rule, devices must be checked annually.

Oregon Health Division Cross-connection Control Rules Top

How do I know when my device needs to be checked ?

The City maintains a database containing all of the permitted backflow devices in Salem. When your device is due to be tested, the City sends out a notice, along with a list of certified local testers. It is then the customer's responsibility to schedule the test. Upon completion of the test and inspection, the customer will be given a copy. Top

Who are the certified backflow device testers for the Salem area?

The City maintains a list of certified local testers. Top