United States
Environmental Protection
Cross-Connection  Control
A  Best  Practices Guide


Target Audience

This Guide discusses the importance of controlling cross-connections
and preventing backflow occurrences from unprotected cross-
connections in the water system.
This Guide is intended for owners and operators of all
systems serving fewer than 10,000 persons.
public water
Kev Cross-Connection Terms and Definitions

Any actual or potential connection between the public water supply and
a source of contamination or pollution.
The flow of water or other liquids, mixtures, or substances into the
distributing pipes of a potable supply of water from any source or
sources other than its intended source. Backsiphonage is one type of
Backflow that occurs when the pressure in an unprotected downstream
piping system exceeds the pressure in the supply piping.
Resulting from negative pressures in the distributing pipes of a potable
water supply.

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                    Cross-connections can occur at many points throughout a distribution system and a
                    community's plumbing infrastructure. Cross-connections can be identified by looking for
                    physical interconnections (or arrangements) between a customer's plumbing and the water
                    system. Some specific examples of backflow incidents that can occur are:

                          Lawn chemicals backflowing (backsiphoning) through a garden hose into indoor
                          plumbing and potentially into the distribution system.

                          Backsiphonage of "blue water" from a toilet into a building's water supply.

                          Carbonated water from a restaurant's soda dispenser entering a water system due to

                          Backsiphonage of chemicals from industrial buildings into distribution system mains.

                          Backflow of boiler corrosion control chemicals into an office building's water supply.

                 Cross-Connection Control and Backflow Prevention
         Why is it Important to Have a Cross-Connection Control and Backflow Prevention Program?

Having a program in place to control cross-connections and prevent backflow is critical to ensuring the safety of the
drinking water you provide to your customers:

       Cross-connections are ever-present dangers that exist in most water systems and can result in serious
        chemical or microbiological contamination events in drinking water systems.

       Cross-connections should be protected in order to prevent backflow, which can be hard to detect.

       In any distribution system, potential cross-connections and therefore sources  of contamination can be numerous,
        varied, and unpredictable.

       Having these programs in place can help you avoid the costs of responding to a contamination incident.

              What Do Cross-Connection Control and Backflow Prevention Programs Involve?

Cross-Connection Control and Backflow Prevention Programs vary by state and municipality.  For more
information, talk with your state primacy drinking water program, state building code or plumbing authority, or health
department.  Cross-Connection Control Programs may involve:

       Authority to implement and enforce a Cross-Connection Control Program.

       Compliance with state or primacy agency plumbing and building codes or plumbing  authority and local

       Public education programs.

       Training  for water system operators and other personnel on hazard surveys; cross-connection identification;
        and backflow device installation, testing, repair, and maintenance.

       Record keeping and reporting.

       Installation  and testing of devices that prevent backflow consistent with the level of hazard.

       Periodic inspection and testing of devices by certified testers.

        How Can  I Start Implementing a Cross-Connection Control and Backflow Prevention Program?

You are responsible for ensuring that the water you provide to customers meets all federal and state standards and
that its quality is not compromised within your distribution system. Developing a comprehensive Cross-Connection
Control and Backflow Prevention Program is one way to ensure the quality of your water and  prevent any  problems that
could occur in your distribution system. If you do not already have a program in  place, consider taking the following

       Contact your state primacy or other agency for more  information on the basic concepts of cross-connection
        control and backflow prevention and information on other water systems in your area that have developed a

       Determine  if you will have to take any legal steps to establish local cross-connection control and  backflow
        prevention  ordinances, with assistance  from your state and local government.

       List the goals for your program in order of priority. For example,  is it more important to develop a public education
        campaign or to conduct a survey of backflow devices at industrial and commercial facilities served by your

       Develop a  proposed timeline for implementing your program.

       Review the plan with your local government, state, and any other key stakeholders.

       Hold public meetings and send notices to customers to educate the community about the need for a program
        and how it  may affect them.

       Plan to monitor your progress in implementing your program and protecting public health.

       Conduct initial hazard testing, as required.

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    Plumbing and
 Distribution System
 Operation Practices
   Hire approved personnel for the installation of any contaminant backflow prevention
   devices to ensure that local codes and manufacturer's recommendations are met.

   Use only assemblies or devices approved by the appropriate state or local authority.

   Test all backflow prevention devices at the frequencies recommended or required by your
   Provide backflow prevention in new construction through coordination with the local
   building inspector's office.
  For existing buildings, develop a program in-house or with plumbing or water system
   personnel to inspect for the adequacy of cross-connection control. Prioritize inspections
   based upon the expected degree of risk.
  Make sure that a backflow inspector conducts inspections for hazards to be controlled.

  For both new construction and existing buildings, require continued inspection and testing
   of backflow devices.
    Fire Hydrant
*  Ensure that construction contractors or anyone using a hydrant to fill a tank intended to
   carry potable water exercises safe fire hydrant connection procedures to prevent backflow.
      What Technologies are Available to Control Cross-Connections and Prevent Backflow?
The type of backflow that is most likely to occur in your system (either from backpressure or backsiphonage) and the
related health effects will determine which backflow prevention technology is best for your water system. The available
technologies are described briefly below.
Atmospheric Vacuum
   Consists of float check, check seat, air inlet port, and possibly a shutoff valve immediately
   Allows air to enter the downstream water connection to prevent backsiphonage.

   Used for backsiphonage conditions only.
  Pressure Vacuum
  Breaker Devices
    Consist of vacuum breakers with a loaded check valve and a loaded air inlet valve.

    Used for backsiphonage conditions only.
 Double Check Valve
   Consist of two independently acting, tightly closing, resilient seated check valves in series
    with test ports.
   Have tightly closing, resilient seated shutoff valves attached at each end of the assembly.

   Prevent backflow under backsiphonage and backpressure conditions.

   Typically approved for only low to medium hazards.
      Air Gaps
    Physical separation between a potable water system and a receiving vessel or source of
    Air gap between the outlet of the potable system and the flood level rim of the receiving
    vessel or any source of contamination must be at least twice  as large as the diameter of
    the potable water outlet and never smaller than 1 inch.
    May require additional pumping downstream of air gap.
    Safest and simplest means under backsiphonage and backpressure conditions.
    Useful for all hazard levels.
  Reduced Pressure
   Zone Backflow
    Similar to the double check valve devices, but also contain an independently acting
    pressure relief valve between the two check valves (which sits lower than the first check
    Protect against high water pollution hazards.
    Protect against backsiphonage and backpressure.

Step 1
Step 2
Step 4
Step 6
Step 7
Step 8
              What Should I Do in Case of a Backflow Event?
Stop the pressure differential that caused backflow of contamination, if possible.

Identify and remove the cross-connection.
Contact appropriate state or local authorities to report the incident.

In areas where public exposure to harmful contaminants is suspected, provide
immediate notice to affected consumers regarding water usage and consumption
and contact appropriate state or local authorities to report the incident. Public
notice should explain the cause of the contamination and corrective actions that
are underway and should include any appropriate health effects language.

Provide updated public notification as appropriate during and after removal of
contamination from the system.
If the contamination is limited to a small area, proceed to step 6.

If the extent of the contamination is unknown or is extensive, proceed to step 4.
(If sampling and testing of the water can be arranged immediately, the results
could be used to determine the extent of the contaminants involved.)
Develop a plan for systematic cleaning or flushing of the system to minimize the
risk of drawing contaminants into uncontaminated areas.

The plan should indicate the amount of water and the length of time needed to
completely flush the system. The direction of flow should draw clean water
through the contaminated site and prevent any contaminated water from entering
uncontaminated areas.  Depending upon the  nature of the contamination, some
wastes may be discharged into the sanitary sewer system and some may need
special handling or treatment.
Throughout the situation, continue to sample within and outside the suspected
contaminated area to assess the extent of the damage.  Skip step 6.
Perform system flushing and, where necessary, cleaning of the customer's
After flushing and any necessary cleaning, test the drinking water in affected
areas to ensure the contamination has been removed.
Ensure that the source of contamination has been removed or that the risk of
contamination has been eliminated using backflow prevention measures that
meet local and state requirements.

 For additional information:
 Call the Safe Drinking Water Hotline at 1 -800-426-4791, visit the EPA Web site at
 www.epa.gov/safewater/smallsys.html, or contact your State drinking water representative.
 Office of Water
                    September 2006