Cross-Connection Control:
A Best Practices Guide
Introduction
This Guide discusses the importance of controlling cross-connections
Purpose and preventing backflow occurrences from unprotected cross-
connections in the water system.
This Guide is intended for owners and operators of all public water
Target Audience
systems serving fewer than 10,000 persons.
Key Cross-Connection Terms and Definitions
Term Definition
Any actual or potential connection between the public water supply and
Cross-connection
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
Backflow
sources other than its intended source. Backsiphonage is one type of
backflow.
Backflow that occurs when the pressure in an unprotected downstream
Backpressure
piping system exceeds the pressure in the supply piping.
Resulting from negative pressures in the distributing pipes of a potable
Backsiphonage
water supply.
Where Can Cross-Connections Occur?
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
backpressure.
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 Programs
Why is it I mportant 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 I nvolve?
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
ordinances.
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 I mplementing 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
steps:
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
program.
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
system?
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.
How Can I Reduce and Prevent Cross-Connections?
Hire approved personnel for the installation of any contaminant backflow prevention
devices to ensure that local codes and manufacturer's recommendations are met.
Plumbing and Use only assemblies or devices approved by the appropriate state or local authority.
Distribution System
Test all backflow prevention devices at the frequencies recommended or required by your
Operation Practices state.
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.
Inspections
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
Connection
carry potable water exercises safe fire hydrant connection procedures to prevent backflow.
Procedures
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.
Technology Description
Consists of float check, check seat, air inlet port, and possibly a shutoff valve immediately
upstream.
Atmospheric Vacuum
Breaker Allows air to enter the downstream water connection to prevent backsiphonage.
Used for backsiphonage conditions only.
Pressure Vacuum Consist of vacuum breakers with a loaded check valve and a loaded air inlet valve.
Breaker Devices Used for backsiphonage conditions only.
Consist of two independently acting, tightly closing, resilient seated check valves in series
with test ports.
Double Check Valve Have tightly closing, resilient seated shutoff valves attached at each end of the assembly.
Devices
Prevent backflow under backsiphonage and backpressure conditions.
Typically approved for only low to medium hazards.
Physical separation between a potable water system and a receiving vessel or source of
contamination.
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
Air Gaps 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.
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
Reduced Pressure
valve).
Zone Backflow
Devices Protect against high water pollution hazards.
Protect against backsiphonage and backpressure.
What Should I Do in Case of a Backflow Event?
Step 1 Stop the pressure di fferenti al that caused backflow of contami nati on, i f possi ble.
Identi fy and remove the cross-connecti on.
Step 2 C ontact appropri ate state or local authori ti es to report the i nci dent.
In areas where publi c exposure to harmful contami nants i s suspected, provi de
i mmedi ate noti ce to affected consumers regardi ng water usage and consumpti on
and contact appropri ate state or local authori ti es to report the i nci dent. P ubli c
noti ce should explai n the cause of the contami nati on and correcti ve acti ons that
are underway and should i nclude any appropri ate health effects language.
Provi de updated publi c noti fi cati on as appropri ate duri ng and after removal of
contami nati on from the system.
Step 3 If the contami nati on i s li mi ted to a small area, proceed to step 6.
If the extent of the contami nati on i s unknown or i s extensi ve, proceed to step 4.
(If sampli ng and testi ng of the water can be arranged i mmedi ately, the results
could be used to determi ne the extent of the contami nants i nvolved.)
Step 4 D evelop a plan for systemati c cleani ng or flushi ng of the system to mi ni mi ze the
ri sk of drawi ng contami nants i nto uncontami nated areas.
The plan should i ndi cate the amount of water and the length of ti me needed to
completely flush the system. The di recti on of flow should draw clean water
through the contami nated si te and prevent any contami nated water from enteri ng
uncontami nated areas. D ependi ng upon the nature of the contami nati on, some
wastes may be di scharged i nto the sani tary sewer system and some may need
speci al handli ng or treatment.
Step 5 Throughout the si tuati on, conti nue to sample wi thi n and outsi de the suspected
contami nated area to assess the extent of the damage. S ki p step 6.
Step 6 Perform system flushi ng and, where necessary, cleani ng of the customer's
system.
Step 7 After flushi ng and any necessary cleani ng, test the dri nki ng water i n affected
areas to ensure the contami nati on has been removed.
Step 8 Ensure that the source of contami nati on has been removed or that the ri sk of
contami nati on has been eli mi nated usi ng backflow preventi on measures that
meet local and state requi rements.
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 EPA 816-F-06-035
