Backflow Tester key terms

Any actual or potential physical link between a potable water system and a source of contamination or pollution, through which nonpotable matter could move into drinking water.

The unwanted reversal of normal flow direction in a piping system, carrying water from an unintended source toward or into the potable supply.

Backflow caused by a drop in supply pressure below atmospheric or below the pressure on the downstream side, which pulls nonpotable water into the piping.

Backflow driven by downstream pressure that exceeds the supply pressure, pushing water backward even though the supply line is still pressurized normally.

Any substance that poses a health hazard when introduced into drinking water, such as toxic chemicals, sewage, or disease-causing organisms.

A substance that degrades the taste, odor, color, or appearance of drinking water but does not by itself create a health hazard.

A condition in which a cross-connection could allow a contaminant that causes illness or death to enter the potable supply.

A physical separation between the lowest opening of a water outlet and the flood-level rim of a receiving vessel, open to atmosphere and never submerged.

The edge of a receptacle, fixture, or tank over which water would spill if the vessel were filled to its maximum intended level.

A drip-proof receptacle or funnel placed below an air gap to catch discharge from a relief valve or drain without creating a submerged inlet.

A device with a float or disc that opens to atmosphere when supply pressure drops, admitting air to break a siphon in a downstream pipe.

A small vacuum breaker attached to a threaded hose outlet or sill cock, designed to prevent backsiphonage through a hose connection.

A testable assembly with a loaded check valve and an air-inlet valve that opens at low pressure, protecting against backsiphonage only and installed above the highest downstream outlet.

A pressure vacuum breaker variant whose air-inlet valve stays closed during normal flow, so it does not discharge water at startup but still resists backsiphonage.

A testable assembly of two independent check valves in series that protects against both backsiphonage and backpressure but only for non-health-hazard conditions.

A testable assembly with two check valves and a hydraulically loaded relief valve between them that discharges if the pressure differential reverses, protecting against health hazards.

The spring- or diaphragm-loaded valve in a reduced pressure principle assembly that opens to discharge water when the zone between the check valves loses its pressure differential.

A valve that permits flow in one direction only and closes automatically to prevent reversal when downstream pressure rises above upstream pressure.

The difference between the upstream pressure and the pressure in the zone between check valves of a reduced pressure principle assembly, which keeps the relief valve closed.

The pressure present in a piping system when no water is flowing, as opposed to the lower pressure observed while water moves through the assembly.

The pressure measured while water is moving through an assembly, typically lower than static pressure because of friction and valve losses.

A small valved port on a backflow assembly body used to connect test gauges and to bleed air or water during a test procedure.

A calibrated pressure gauge, often with a mirrored dial and fine gradations, used with test kits to read pressures at assembly test cocks accurately.

The closeness of a test gauge reading to the true pressure, usually expressed as a percentage of full scale and verified by periodic calibration.

The documented comparison and adjustment of a test gauge against a known reference standard so its readings fall within accepted tolerance.

To release air or water from a test cock or gauge line so that a stable, accurate pressure reading can be obtained.

The movable sealing element inside a check valve that seats against the valve body to stop reverse flow.

The machined surface in a valve body against which the disc or closure element seals to stop flow.

The float- or disc-operated opening on a vacuum breaker that admits air into the assembly when internal pressure approaches atmospheric.

In a reduced pressure principle or double check assembly, the upstream check valve that closes against reverse flow from the intermediate zone.

The downstream check valve in a testable assembly, which blocks reverse flow from the downstream piping into the intermediate zone.

A cross-connection control strategy that isolates an entire facility or premises at the service connection with one or more testable assemblies.

A cross-connection control strategy that protects individual fixtures, appliances, or processes inside a building with dedicated backflow preventers.

Installation of a backflow prevention assembly on the service line where it enters a property, protecting the public main from on-site hazards.

The classification, typically health hazard or non-health hazard, assigned to a cross-connection based on the type of material that could backflow.

The required periodic field verification that a testable backflow assembly still meets its design performance standards, usually performed by a certified tester.

The written record of an assembly test listing the assembly type, serial number, gauge readings, pass or fail result, tester identity, and date.

A person who has completed approved training and passed an examination authorizing them to test backflow prevention assemblies in a jurisdiction.