Cross Connection and Backflow Prevention

Federal and State regulations require public potable water supplies to adopt rules to prevent contamination in their water systems. To comply with these mandates, the City of Garden Ridge City Council has adopted an ordinance; the Cross Connection Control and Backflow Prevention Program, to protect the City’s potable water supply from contaminants back-flowing from a customer’s water system (see Ordinance 54).

Accredited Backflow Prevention Assemblies Testers List


Frequently Asked Questions

What is a cross-connection?

A cross-connection is an actual or potential connection between a public water system or consumer’s potable (i.e., drinking) water system and any other 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. A direct cross-connection is a cross-connection which is a subtract to both back-siphonage and backflow and indirect cross-connection is a cross-connection which is a subject to back-siphonage only.

What is backflow?

Backflow is the undesirable reversal of flow of water or other substances into the public water system or consumer’s potable water system. There are two types of backflow... backpressure backflow and back-siphonage.

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.

  • Causes of increases in downstream pressure: Pumps (such as wells and booster pumps), temperature increases in boilers, etc.
  • Causes of decreases in downstream pressure: Water line flushing, fire fighting, or breaks in water mains.

What is back-siphonage?

Back-siphonage is backflow caused by in a Public water system or consumer’s potable water system. The effect is similar to drinking water through a straw. Back-siphonage can occur when there is a stoppage of water supply due to a nearby fire fighting, a break in a water main, etc.

Why does the Water Department need to control cross-connections and protect its public water system against backflow?

Backflow into a public water system can pollute or contaminate the water in that system making it unsafe to drink. Each water supplier has a responsibility to provide water that is usable and safe to drink under all foreseeable circumstances. Furthermore, consumers have faith that water delivered to them through a public water system is safe to drink. Therefore, the Water Department must take precautions to protect its public water system against backflow.

What should a water supplier do to control cross-connections and protect their public water systems against backflow?

The Texas Commission on Environmental Quality gives public water suppliers two options:

  • Require backflow prevention at each service connection that may create a threat to the public water supply.
  • Require backflow devices and assemblies within a premise as outlined the state required plumbing codes.

The water suppliers usually do not have the capability to repeatedly inspect every consumer’s premises for cross-connections and backflow protection. 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; (3) premises exempt from the State Plumbing Code inspection and premises where an internal backflow preventer required under the State Plumbing Code is not properly installed or maintained; (4) classified or restricted facilities; and (5) tall buildings.

What is a backflow preventer?

A backflow preventer is a means or device which prevents pollutants and contaminants from flowing into the public water system.

What is an air gap?

An airgap 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 on 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.

What is a reduced pressure zone assembly?

A reduced pressure zone assembly protects water from substances that may contaminate water causing illness or death.

A sprinkler/irrigation system requires this device. It is also commonly used in commercial establishments to protect against numerous contaminants. These devices must be installed above ground.

What is a hose bibb vacuum breaker?

A hose bibb vacuum breaker (HBVB) is one of the least expensive and most commonly used backflow preventers required by codes. When attached to an outside water tap, these backflow preventers keep water that may be contaminated with fertilizer or insecticide from entering your drinking water. HBVB is non-testable.

You should attach an HBVB if you have a sprayer on your hose.

Why do backflow preventers have to be tested yearly ?

In order to insure the proper operation of a backlfow assembly, it must be tested and certified upon installation and annually thereafter as required by state code.

The Texas Commission on Environmental Quality oversees the state requirements.