ASSE 5120 key terms

Any actual or potential physical link between a potable water supply and a source of contamination or pollution, through which backflow could move undesirable substances into drinking water.

The unwanted reversal of water flow from its intended direction, carrying nonpotable water, gases, or suspended solids into a potable piping system.

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

Backflow resulting from downstream pressure that exceeds the pressure of the potable supply, pushing water backward through a cross-connection.

The introduction of any substance into potable water that degrades its quality or appearance but does not create a hazard to health, such as taste, odor, or color changes.

The introduction of a substance into potable water that creates a hazard to health, including disease organisms, toxic chemicals, or other harmful material.

A physical separation between the free-flowing discharge end of a supply pipe and the flood-level rim of a receiving vessel, providing the highest degree of backflow protection.

The edge of the receptacle from which water would overflow if the receptacle were filled to its maximum working capacity, used as the reference point for air gap measurement.

A testable assembly with two independently acting check valves and a hydraulically operating differential relief valve, used where both backsiphonage and backpressure health hazards exist.

A testable assembly of two independently acting check valves, used to protect against backflow where only a pollution hazard, not a health hazard, exists.

A testable device with a spring-loaded check valve and an air-inlet valve that opens to atmosphere when supply pressure drops, protecting against backsiphonage only.

A non-testable device with a float-operated air-inlet valve that admits air when supply pressure falls, used on noncontinuous-pressure applications for backsiphonage protection only.

A valve that permits flow in one direction only and closes automatically to prevent reversal, forming a core component of many backflow prevention assemblies.

The hydraulically operated valve in a reduced pressure principle assembly that discharges water to atmosphere to maintain a pressure differential between the two zones.

The difference in pressure between two points in a piping system; in an RP assembly, the relief valve maintains the first zone at least a set amount above the second.

The pressure exerted by water at rest in a system, measured perpendicular to the pipe wall and unaffected by flow velocity.

The pressure remaining at a point in a piping system while water is flowing, reflecting losses caused by friction and elevation.

The reduction in pressure caused by water rubbing against pipe walls, fittings, and valves as it flows through a system.

A measure of pressure expressed as the height of a water column it can support, where one pound per square inch equals about 2.31 feet of water.

A pressure surge caused by sudden stopping or reversal of flow, which can damage piping and backflow assemblies and may create temporary backpressure conditions.

The increase in water volume as it is heated in a closed system, which raises pressure and can cause relief valve discharge or stress on backflow assemblies.

The classification of a cross-connection risk as either a health hazard or a pollution hazard, which determines the minimum type of backflow protection required.

Backflow protection installed at the service connection or property line to isolate the entire premises from the public water system.

Backflow protection installed at an individual fixture, appliance, or point of use to protect a specific cross-connection within a building.

A small valved opening on a backflow assembly used to attach test equipment, bleed air, and read pressure at specific points during field testing.

A test instrument with two hoses that measures the difference in pressure between two points, used to verify check valve and relief valve operation.

The on-site procedure performed with gauges and test cocks to confirm that a backflow assembly meets its required performance criteria at installation and annually thereafter.

The recurring testing and inspection of a backflow assembly required by regulation, typically every twelve months, to confirm continued proper operation.

The written record of a field test documenting assembly type, serial number, gauge readings, pass or fail result, tester identity, and date of service.

The periodic verification and adjustment of test instrument accuracy against a known reference, ensuring field readings are reliable and defensible.

A person who has completed recognized training and passed an examination, and who holds current credentials authorizing performance of backflow assembly field tests.

The practice of protecting a water system at the boundary of each customer property so that contamination originating inside cannot reach the public main.

The organized set of policies, surveys, device requirements, testing schedules, and records a water purveyor uses to prevent contamination of its distribution system.

A device that opens to admit air into a system when internal pressure falls below atmospheric, preventing backsiphonage in tanks and heaters.

A testable vacuum breaker designed with a check valve arrangement that limits discharge from the air inlet during normal operation, used for backsiphonage health hazards.

A written account of an unusual event such as assembly discharge, injury, or property damage, prepared promptly and retained for liability and compliance purposes.

Gear such as gloves, eye protection, and hearing protection worn during testing to reduce exposure to pressurized water, chemicals, and physical hazards.