Glossary.

A

Air-gap

The physical separation, vertical, between a water outlet and the flood-rim of the receptacle below it. The cleanest cross-connection protection: no mechanical device, no failure mode. SPS 382 requires a minimum air-gap of twice the outlet diameter or 1″, whichever is greater.

AHJ

"Authority Having Jurisdiction." In Milwaukee that's the city water utility (MWW) plus, depending on context, the state plumbing inspector (WI DSPS) and the local fire marshal. We file every test report with the correct AHJ same-day.

ASSE 5110

The American Society of Sanitary Engineering Series 5000 standard for the qualifications of a Backflow Prevention Assembly Tester. Required in Wisconsin. Held by all three of our testers.

B

Back-pressure

The reversal of flow caused by downstream pressure exceeding supply pressure. Sources: thermal expansion (heating a sealed tank), pumping (booster pump downstream), elevation (a tank on the roof), gas charge (CO₂ in a carbonator).

Back-siphonage

The reversal of flow caused by a drop in supply pressure below downstream pressure (often near atmospheric). Sources: water-main break, fire-flow withdrawal, water-tower drawdown, a closed valve upstream of an open one.

Bridge

An informal term for a continuous unbroken pipe between potable supply and a fixture; the path along which backflow could travel. Cross-connection protection breaks the bridge mechanically.

C

Check valve

A spring-loaded one-way valve that closes against reverse flow. The fundamental component of every backflow assembly except the air-gap.

Cross-connection

Any actual or potential connection between potable water and a substance other than potable water. The substance may be water of unknown quality, a chemical, a gas, or a non-potable liquid. The cross-connection exists whether or not a backflow event has occurred.

Containment

Backflow protection installed at the water-service entrance to a premises. Protects the utility's main from anything in the building. SPS 382 requires containment on every commercial premises.

CK-1 / CK-2

The first and second check valves inside an RP or DC assembly. CK-1 is upstream; CK-2 downstream. Both must seat tightly during the annual test.

D

DC

Double Check Valve Assembly. ASSE 1015. Moderate-hazard protection. Two checks in series, no relief vent. Data sheet.

DCDA

Double Check Detector Assembly. ASSE 1048. A DC with a parallel 5/8″ low-flow meter, used on fire service without antifreeze. Data sheet.

Detector assembly

Any backflow assembly with a parallel low-flow meter to log unauthorized tap or slow leak. Used on fire service. RPDA and DCDA.

F

FCCCHR

The Foundation for Cross-Connection Control and Hydraulic Research at the University of Southern California. Maintains the national list of approved backflow assemblies and publishes the field's working manual.

Flood-rim

The horizontal plane that water reaches when the receptacle (sink, tank, basin) is full and about to overflow. Air-gap dimensions are measured to the flood-rim, not the bottom of the spout.

H

Hazard class

The classification of a cross-connection by the consequence of a backflow event. High: toxic / health threat (chemicals, biological, sewage). Moderate: aesthetic or non-toxic (heating loop without chemicals, plain potable in a sealed tank). USC FCCCHR §3.4 prescribes the classification.

Hose bibb

An exterior or wall-mounted faucet with hose threads. By itself a common back-siphonage hazard (a hose attached to a chemical jug is the textbook example). A hose-bibb vacuum breaker is the cheapest protection; an SVB or DC isolation is the more durable answer for commercial premises.

I

Isolation

Backflow protection at an individual fixture rather than the building service entrance. Protects the building's interior potable water from one specific hazard. SPS 382 requires isolation at every interior cross-connection above its threshold; the threshold is set by hazard class.

P

PVB

Pressure Vacuum Breaker. ASSE 1020. A single check plus an air-inlet vent above flood-rim. Protects against back-siphonage only. Data sheet.

Premises

The legal term in SPS 382 for a single water-service customer site. A commercial building is typically one premises; a campus is typically one premises per service.

Potable

Water meeting EPA SDWA standards for human consumption. The water in the city main is potable. The water inside your boiler may not be.

R

RP

Reduced Pressure Principle Assembly. ASSE 1013. The high-hazard family. Two checks plus a vented intermediate zone. Data sheet.

RPDA

Reduced Pressure Detector Assembly. ASSE 1047. An RP with a parallel 5/8″ meter, used on high-hazard fire service. Data sheet.

Relief vent

The atmospheric vent on an RP that opens when the intermediate zone's pressure rises within 2 psi of supply. The third line of defense.

S

SOV

Shutoff valve. The two ball valves (SOV-1 inlet, SOV-2 outlet) that frame every backflow assembly. The tester closes them to isolate the assembly during the annual test.

SVB

Spill-Resistant Vacuum Breaker. ASSE 1056. A PVB with a secondary check that prevents start-up dribble; indoor applications. Data sheet.

T

Test cock

The 1/4″ ball-valved port on an assembly's body that the tester connects the gauge to. Typically four on an RP (TC#1 through TC#4), three on a DC, two on a PVB/SVB. The tester opens them in a specific sequence per the assembly type.