Backflow Tester cheat sheet

Cross-connection: any actual or potential physical connection between a potable water system and any source of nonpotable fluid or substance.

Backsiphonage is caused by negative or sub-atmospheric pressure in the supply; backpressure is caused by downstream pressure exceeding supply pressure.

Pollution hazard degrades quality (aesthetic, no health risk); contamination hazard creates a health hazard and requires a higher protection level.

Air gap is the only non-mechanical protection; minimum separation is two times the effective opening diameter, never less than 1 inch, and the gap must be above the flood-level rim.

An atmospheric vacuum breaker may not be installed under continuous pressure (no downstream shutoff) for more than 12 hours; it has no test cocks and cannot be field-tested.

A pressure vacuum breaker must be installed at least 12 inches above the highest downstream outlet; a spill-resistant PVB is required where the device could be flooded.

A reduced pressure principle assembly provides protection against both backsiphonage and backpressure and may be installed where backpressure exists; it discharges water from the relief port when a differential of about 2 psi is lost.

A double check valve assembly protects against backpressure and backsiphonage only for non-health-hazard (pollution) conditions and is not permitted for contamination hazards.

A hose-bibb vacuum breaker must not be under continuous pressure and must not have a shutoff downstream; a dual check is used only as a low-hazard, non-testable device at the meter or appliance.

Differential pressure check: close test cock 2, open high side to upstream and low side to downstream; a passing check holds a differential that does not drop below 1.0 psi (RP relief check) or the manufacturer's specified minimum.

RP assembly test sequence: check 1 differential, then check 2 differential, then relief valve opening point; the relief valve must open when the inlet pressure is reduced to a differential of 2.0 psi or more.

RP relief valve opening point is confirmed by bleeding the low side until the relief discharges, then noting the pressure differential at which discharge begins (typically 2.0 psi minimum).

DC assembly test: record static line pressure, then measure check 1 and check 2 differentials; each check must hold at least 1.0 psi and the device must not leak past either check.

PVB test: record line pressure, then measure the air-inlet opening point; the air inlet must open when the differential drops to 1.0 psi or greater.

Test gauges must be calibrated at least annually, have a range appropriate to the line pressure, and be connected with the high side to upstream and the low side to downstream of the check being tested.

Record on the test report: assembly make, model, size, serial number, location, static pressure, each differential or opening point, pass/fail, tester name, certification number, and date.

A failed assembly must be tagged, reported to the water purveyor and property owner, and either repaired by a licensed technician and retested or replaced; a failed device is not left in service.