This page includes detailed, need-to-know, information for residential water customers.
Cross-Connection – is the physical connection between the potable (drinking) water system and an “end-use” (water utilizing fixture, equipment, or process) where a potential water contaminating hazard exists.
Backflow – is the undesired reverse flow of contaminants into the potable water from an “end-use” hazard and is typically driven by common, but unfavorable, hydraulic events in either the public or a private water distribution system.
Explaining Cross Connection and Backflow Prevention - A Comprehensive Informational Page
Frequently Asked Questions (FAQ’s)
List of licensed plumbing firms
Modern plumbing fixtures generally have built-in backflow protection. For instance, a faucet spout terminates above the flood rim level of the sink or tub. So if the sink or tub is full of dirty water or worse, backed-up sewage, there is no possible way for a backflow because of the air gap created by the elevated spout. Toilet fill valves, clothes washers, dishwashers, and refrigerator/ice makers also employ some type of built-in air gap as their method of protection.
Hand Held Sink or Shower Spray Heads
Hand held shower heads are required to be protected against backflow in one of two ways:
Vacuum Breakers and Dual Check Valves are considered “non-testable” and may be installed or replaced by a homeowner.
Kitchen and lavatory faucets, constructed within the US, with integral or auxiliary spray heads, generally do not need additional backflow prevention devices.
Hose Bibb and Garden Hose Usage
Because of their portability and universal ease of connection, general purpose/garden hoses pose one of the greatest risks for backflow occurrences. In addition, there is a general complacency (underestimation of hazard level), with what hoses are connected to or with what they are left submerged in.
In residential applications, the normal way to protect the drinking water system from the hose, and its uses, is to outfit the hose bibb (spigot/valve) with a vacuum breaker. Hose bibbs are available with integral vacuum breakers or vacuum breakers can be purchased separately and screwed directly onto the outlet threads of the bibb. In this case, the vacuum breaker, in turn, has hose threads to connect the hose to. Vacuum breakers are very inexpensive but provide a very good level of protection against backflow.
Every hose bibb, regardless of age or usage, must be outfitted with a vacuum breaker meeting the product standard/listing ASSE 1011 or ASSE 1019.
Vacuum Breakers are considered non-testable and may be installed or replaced by a homeowner.
In-ground Irrigation and Lawn Sprinkler Systems
Automatic irrigation systems pose a significant threat to the drinking water system. By their nature, sprinkler heads may reside in a pool of yard/animal waste, pesticides and/or fertilizers. And because the supply lines are under constant pressure and flow, and controlled by underground control valves, a typical vacuum breaker is not an appropriate form of protection against backflow. There are two types of backflow prevention assemblies allowed:
PVB may be winterized in place; RP’s must be removed and placed in a warm storage area. Both assemblies require their annual test at the time of spring seasonal start-up.
Installation, repair, replacement and/or annual testing must be performed by a plumbing services firm (licensed plumber). Their plumbers must be at least of the “Journeyman” license level and also possess a separate cross connection technician certification. Do not be afraid to ask for proof!
Hint for owners with irrigation systems: make the testing part of your spring start-up contract. The irrigation firms may be able to procure the most favorable pricing due to their ability to deal in volume with plumbing services firms.
Since their inception, residential fire sprinkler systems have been supplied with water by three different piping arrangements. The following describes the details of each variation:
Where water is connected to a heating system boiler as a make-up water supply, it must be protected by a dual check valve with integral vent (standard no. ASSE 1012). This device is considered “non-testable” and must be replaced every five years. If chemicals are added to the heating water system (this is not common), an ASSE 1013 must be installed and special provisions for drainage need to be considered and yearly testing by a plumber is mandatory.
Dark Room Sinks and Automatic Film Developers
Not a very common item for any household and with the advent of digital photograph, photo developers and sinks are certainly a rarity these days. But when connected to the water distribution system, backflow prevention is a must. If connected to a tank or sink, a “non-testable” device (standard no. ASSE 1012), may be utilized. If chemical injection is present or an automatic developer is used, a “testable” assembly (standard no. ASSE 1013), must be installed and special provisions for drainage need to be considered and yearly testing by a plumber is mandatory.
Consult with a licensed plumber regarding proper connection and protection requirements or contact a WSSC inspector by phone or email: 301-206-8886 or plansreview@wsscwater.com.
Understanding and respecting the risk of water contamination is a great start, when in doubt, seek help. Basic guideline: every water outlet needs some form of protection; get to know what is needed.
Have “non-testable” backflow devices replaced at the intervals described above. Have “testable” backflow assemblies tested yearly (bi-yearly for fire sprinkler systems) and rebuilt or replaced as needed (usually every 5-8 years).