Backflow / Cross Connections


It is the responsibility of the City of Andrews to protect its drinking water supply by instituting and enforcing a cross connection program.  The program includes the installation of backflow prevention assemblies.

In 2000, the City of Andrews initiated a state-mandated backflow prevention ordinance as required by Chapter 291 of the Utility Regulations for the continuance of water service to protect the public potable water supply from the possibility of contamination by isolating such contaminates within the customer's internal distribution system.

When new water service is established, our service technician will meet the customer at their new location to inspect the home or business. The technician will check all outside faucets as well as bathroom toilets to ensure backflow devices are in place. If a sprinkler system is installed, a certified inspector must test the system for compliance.  

Bi-annual testing of backflow protection assemblies are required by a certified tester  registered with the City of Andrews. You can obtain a list of approved backflow prevention assemblies here.

It is a logical assumption that because water is always under pressure, it can only flow in one direction.  However, it is possible for the flow to be reversed.  Water will always flow towards the point of lowest pressure.  If a main line in our system should break, or if a fire occurred and the fire department opened several hydrants, the pressure in our water mains could drop dramatically, causing a reversal of flow. The potential for this reversal of flow is why our department is concerned about the possibility of backflow of contaminants into our water system.

Backflow Prevention
Preventing backflow is an important part of maintaining a healty water supply. The City of Andrews water distribution system is designed to carry water from the plant to the consumer. Due to cross-connections the water distribution system is susceptible to backflow.

There are two types of backflow:
Backpressure backflow:  Occurs when an unprotected water line is attached to the container or pipes holding pressurized material the material may be “pumped” back into the potable water system.

Backsiphonage:  Occurs when the pressure in the distribution system drops, siphoning water from the consumers’ system into the distribution system.   

Vacuum_Breaker_Faucets     Vacuum_Breaker_Toilet

Either of these conditions will cause any substance that may be in contact with the water system to be directed back into the potable water supply.

There are two devices used to prevent backflow for Irrigation systems.

Backflow_Pressure_Vacuum_BreakerPressure Vacuum Breaker
This device is approved for irrigation systems; however, it is rarely used because of above ground installation and is subject to freezing during winter months. This device is also approved for chemical injection systems on sprinklers. Irrigation system can be turned off at 1 of 2 shut off handles.


Backflow_Atmospheric_Vacuum_BreakerAtmospheric Vacuum Breaker 

This device is commonly found on older sprinkler systems but is not approved for new installations because it is non-testable. It must be replaced when upgrading your irrigation system. No shut off handles to isolate the irrigation system.

Backflow_rpz_assemblyRPZ - Reduced Pressure Zone
This device is designed for high hazard applications with a possibility of back pressure in addition to back siphonage.

Simple Steps to Prevent Backflow:

  • Guard against cross-connections. A garden hose is a direct connection to the drinking water in your home.
  • Don't attach chemical sprayers or leave a garden hose submerged in a swimming pool.
  • Make sure backflow prevention device is installed on your home sprinkler system