Skip to main content

Backflow and Cross-Connection Control

What is a Cross-Connection?

A cross-connection is a point in a plumbing system where the potable (drinking) water supply is or can be connected to a non-potable source (water not intended for drinking). There are two types of cross-connections, direct and indirect. A Direct Cross-Connection is a connection on a potable water system by a non-potable pressurized line such as irrigation lines, boiler lines, chemical transfer lines, etc. An Indirect Cross-Connection is a connection on a potable water system by a line, or hose, and is usually open at one end. Examples of Indirect Cross-Connections are garden hoses, sprinkler systems, water softeners, bath tubs, showers, wash basins, etc. Some examples of Indirect Cross-Connections made with a garden hose are:

  • A garden hose attached to a pesticide/chemical spray bottle.
  • A garden hose filling a pool with the downstream end of the hose being submerged by the non-potable water.

How do you prevent Cross-Connections?

You can help keep our drinking water safe from contaminates easily by following these simple precautions:

  • Be aware of and eliminate Cross-Connections.
  • Install approved Backflow assemblies, devices, or air gaps on any system that contains contaminated water.
  • Install hose bib vacuum breakers on water fixtures. Without proper protection something as useful as your garden hose has the potential to contaminate your home’s water supply. In fact, according to the American Backflow Prevention Association, over half of the nation’s Cross-Connections involve unprotected garden hoses.

What is a Backflow?

Backflow occurs when water that has already entered a facility flows back into the public water system. There are two causes of Backflow, or water flowing back into the public water system:

  • Backsiphonage – a reversal flow of water that occurs when a Cross-Connection is present and the pressure in a water main is reduced or drops to a negative pressure. Backsiphonage is created when water mains experience a sudden drop in water pressure due to water main breaks and shutdowns, nearby firefighting efforts, etc.
  • Backpressure – a reversal flow of water that occurs when the customer’s pressure is higher than the water main pressure. Backpressure occurs when heating systems, elevated tanks and pressure-producing systems create pressure in your plumbing that exceeds the water main pressure.

    How do you prevent Backflow?

    Install approved Backflow assemblies, devices, or air gaps on your water system. A Backflow prevention assembly is a testable, mechanical device that uses check valves to prevent polluted or contaminated water from flowing backwards. Some assemblies eliminate backflow by discharging used water to the ground. Assemblies installed as a secondary protection should be located as close as possible to the water meter.

    Can check valves be used as a Backflow prevention assembly?

    No. A check valve is not equipped with test connections to assure that the valve is preventing backflow.

    What is an approved Backflow assembly?

    An approved assembly is any type of backflow prevention assembly that has been tested and approved by an independent testing laboratory.

    Which Backflow assemblies can be used within GHID?

    Any backflow prevention assembly may be used that has been tested by an independent testing laboratory and accepted by the Utah Division of Drinking Water. However, it must be the appropriate assembly for the degree of health hazard at your facility.

    If my building was recently modified to meet city code requirements by installing Backflow assemblies internally, do I still need them at the service connection?

    Under certain health hazard conditions, yes. Even though plumbing code provisions may be rigidly enforced on new installations, experience has shown that “on-site” modifications and alterations of private plumbing are common. Possible hazards to the public water system can be created due to backflow from private plumbing. These hazards may be caused by a submerged hose, complex mechanical failure, etc. In most cases, the only practical way to assure protection is to install a backflow assembly at the point of service delivery. That way, regardless of what happens inside the customer’s property or what changes are made to private plumbing, the public water system is protected.

    What assembly(ies) should we have installed to be legal as well as responsible?

    To determine what is required of your facility, have your Registered Licensed Professional Engineer refer to the Utah Division of Drinking Water Rules and Regulations to determine the health hazard risk level of your facility and corresponding Backflow assembly requirements.

    Thermal Expansion Control (Section 607.3 of the Utah Plumbing Code)

    Where a storage water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion tank shall be connected to the water heater cold water supply pipe at a point that is downstream of all check valves, pressure reducing valves and backflow preventers. Thermal expansion tanks shall be sized in accordance with the tank manufacturer's instructions and shall be sized such that the pressure in the water distribution system shall not exceed that required by Section 604.8.

    Expansion Tank FAQ

    •  What is a thermal expansion tank? An expansion tank is a small tank that is attached to the inlet cold-water supply pipe of a water heater. 
    • Why do I need an expansion tank? Water expands when heated, creating increased pressure in a water heater. In the absence of an expansion tank, the water will look for a way to escape. In older systems, the hot water will back flow through the cold-water pipe through which it came and end up back into the public water supply.  Backflow can lead to contamination of clean water. The national plumbing codes mandate a backflow preventer. Because of the backflow preventer, the water has nowhere to go except the pressure relief valve located on your water heater.  If your relief valve is working properly, it will spill water onto the floor. The expansion tank provides a pressurized air cushion that absorbs expanded water, keeping pressure in the system within safe levels. If left unchecked, the constant fluctuations in water pressure will damage the heater and associated piping.
    • How soon will Granger-Hunter Improvement District install a backflow device at my water meter? In the future, GHID plans to install a backflow device at every connection.  With over 27,500 connections, this will take some time.  Before a backflow device is installed at the meter, GHID will deliver a letter giving 30 days’ notice.  However, if there is an emergency repair from a leak on the system, GHID will not be able to give advanced notice.  In this case, a notice will be given immediately following the repair.
    • Where can an expansion tank be purchased? Expansion tanks can be found on-line or at any home-improvement or plumbing supply store if you are installing it yourself.  Tanks range from $40-70.  If you choose to have a certified plumber install an expansion tank, it may range from $200 - $400.  We recommend getting multiple quotes before hiring a plumber.
    • Do water heater manufacturers specify a need for an expansion tank? Yes, all water heater manufacturers state a similar requirement to maintain warranty coverage if the system contains a one-way device like a backflow preventor.
    • Is it necessary to install an expansion tank on a tankless water heater? Plumbing code does not require an expansion tank with a tankless water heater unless a storage tank is added to the tankless heater in a closed system. 

    Indirect/Special Waste (Section 608.1 of the Utah Plumbing Code)

    A potable water supply system shall be designed, installed and maintained in such a manner so as to prevent contamination and pollution from nonpotable liquids, solids or gases being introduced into the potable water supply through cross connections or any other piping connections to the system. Backflow preventer applications shall conform to Table 608.1, except as specifically stated in Sections 608.2 through 608.16.10.


    Additional Info

    *Please call GHID's Cross-Connection Control and Backflow Prevention personnel at 801.955.2283 for more info.

    **Visit the American Backflow Prevention Association for more information.

    Join our mailing list