ASSE 5110 key terms

Any actual or potential physical connection between a potable water supply and a source of contamination or pollution that could allow non-potable fluid to enter the drinking water.

The unwanted reverse flow of water or other fluid from a non-potable source into the potable water distribution system, occurring by either backsiphonage or backpressure.

Backflow caused by negative or sub-atmospheric pressure in the supply piping, which draws non-potable fluid through a cross-connection into the potable system.

Backflow caused when downstream pressure exceeds supply pressure, pushing non-potable fluid backward into the potable system, often from pumps, boilers, or elevated piping.

Any substance that, if introduced into drinking water, could cause illness, injury, or death, as opposed to a pollutant, which only affects taste, odor, or appearance.

An unobstructed vertical physical separation between the lowest point of a potable water outlet and the flood-level rim of the receiving vessel; it provides the highest degree of cross-connection protection.

The edge of a receiving vessel, fixture, or tank over which water would overflow, used as the reference point for measuring air gap separation.

A testable assembly containing two independently acting spring-loaded check valves with a hydraulically operated differential relief valve between them, used for high-hazard protection.

A reduced pressure principle assembly combined with a meter and bypass that detects low flows, used on fire lines where high-hazard protection and flow measurement are both needed.

A testable assembly of two spring-loaded check valves in series used for low-hazard protection; it has no relief valve and cannot discharge to atmosphere.

A double check valve assembly combined with a bypass and detector meter, commonly installed on fire protection systems to reveal leaks or unauthorized water use.

A testable vacuum breaker with a spring-loaded check and an air inlet that opens at low supply pressure; it must be installed above downstream piping and cannot be under continuous pressure.

A spill-resistant vacuum breaker similar in function to a pressure vacuum breaker but designed not to spill water during normal operation, so it may be used where discharge is objectionable.

A non-testable vacuum breaker with a float-operated air inlet and no spring; it must be downstream of the last control valve and cannot be under continuous pressure.

A small non-testable, non-removable device threaded onto a hose bibb to stop backflow through the hose by admitting air during backsiphonage.

A non-testable, non-removable assembly of two check valves used on low-hazard residential or appliance connections where routine field testing is not required.

A fixed inverted U of piping rising at least 35 feet above the highest downstream outlet, which prevents backsiphonage by keeping an air column but gives no backpressure protection.

A one-way valve that permits flow in one direction only and closes to stop reverse flow; it is the basic working component of every mechanical backflow preventer.

The hydraulically operated valve in a reduced pressure principle assembly that opens to atmosphere when the pressure differential between the two check valves falls below a set minimum.

A small numbered quarter-turn valve installed on a backflow assembly, used to connect test equipment and to apply or read pressure at specific points during field testing.

A clear plastic or glass tube on test equipment that lets the tester see water discharge or air movement, confirming a valve has opened during a test.

An instrument that measures the difference between two pressures, used to verify the pressure drop across check valves and the opening point of a relief valve.

A field test in which pressure is applied to one side of a check valve and watched for a set period to confirm the valve seals and holds.

The pressure differential at which the differential relief valve of a reduced pressure assembly opens and begins discharging water to atmosphere.

The vacuum or pressure condition at which the air inlet of a vacuum breaker opens, admitting air to break the vacuum and stop backsiphonage.

An organized local effort combining surveys, regulations, device installation, periodic testing, and recordkeeping to keep contaminants out of the potable water system.

Protecting the public water distribution system at the service connection or property line so contamination originating on a premises cannot reach the water main.

Protecting potable water inside a building by installing backflow protection at each point of use or at the branch serving a hazardous fixture or process.

A classification of the risk a cross-connection poses, separating health hazards involving toxic or illness-causing substances from non-health hazards that affect only aesthetics.

A cross-connection that could introduce contaminants able to cause illness, injury, or death, requiring the highest protection such as an air gap or reduced pressure assembly.

The agency or official that enforces cross-connection control rules, approves devices and installations, and reviews test reports submitted for a water system.

The periodic field verification, typically every twelve months or as the local program requires, that a testable assembly's check valves and relief valve function correctly.

The pressure rise created when water is heated in a closed system that has no provision for expansion, capable of damaging assemblies, check valves, and plumbing.

A pressure surge produced by a sudden change in water velocity, capable of damaging check valves, seat discs, and gauges unless controlled by arrestors or slow-closing valves.

The buildup of debris, scale, or mineral deposits on a check valve seat or disc, a frequent cause of leakage and failed tightness tests.

A manufacturer-supplied set of replacement parts such as seats, discs, springs, and O-rings, used to restore a backflow assembly to reliable working condition.

The documented verification, usually performed annually, that field test gauges read within the allowed tolerance when compared with a certified reference standard.

A person who has passed an approved competency examination and holds current credentials permitting them to field test backflow prevention assemblies in a given jurisdiction.

A standardized record documenting assembly type, size, location, serial number, test results, and tester certification details, submitted to the water supplier or authority.