Free Backflow Tester Exam Flashcards

Backflow is unwanted reverse flow from a nonpotable or questionable source into the potable water system. It can happen by backpressure or backsiphonage.

Backpressure occurs when downstream pressure exceeds supply pressure and pushes water backward. Pumps, boilers, elevated tanks, and pressurized systems can create it.

Backsiphonage occurs when negative or reduced supply pressure pulls water backward from a connected source. Main breaks and heavy demand can create this condition.

A cross-connection is any actual or potential connection between potable water and a nonpotable source. Cross-connections are where backflow hazards begin.

Contamination is a health hazard that can cause illness or death. Pollution affects water quality or aesthetics but is not usually a direct health hazard.

Containment protects the public water system at the service connection. Isolation protects internal plumbing by controlling specific hazards within a facility.

An air gap is a physical separation between a water outlet and flood-level rim. It is the simplest and most reliable backflow prevention method when installed correctly.

The Safe Drinking Water Act is the federal law behind drinking-water protection standards. Water purveyors operate cross-connection programs to protect the public supply.

The water purveyor is responsible for protecting the public water system. That includes surveys, assembly requirements, testing records, and enforcement under local rules.

A tester verifies installation details, performs approved field tests, records actual results, reports failures, and avoids returning a failed assembly to service as acceptable.

One cubic foot of water weighs about 62.4 pounds and contains about 7.48 gallons. These constants support basic hydraulic calculations.

One psi is approximately 2.31 feet of water head. This conversion links pressure readings to elevation differences.

Static pressure is measured with no flow. Dynamic pressure is measured while water is moving and includes losses from friction and demand.

Pressure loss occurs as water moves through pipe, fittings, valves, and assemblies. Higher flow, smaller pipe, roughness, and restrictions increase loss.

Water speeds up through a restriction and pressure drops. That pressure drop can contribute to backsiphonage at improperly protected connections.

A reduced pressure principle assembly has two independently acting check valves and a differential pressure relief valve between them. It protects against backpressure and backsiphonage for high hazards.

The relief valve provides a visible warning and discharge path when zone pressure rises or differential pressure drops. Continuous discharge usually means a check or pressure problem.

Local practice content uses 5.0 psid as the minimum pressure drop across RP check valve #1 for a passing field test.

Local practice content uses 2.0 psid as the minimum relief-valve opening point for an RP assembly to pass.

A common USC-style RP sequence is check valve #1, relief valve opening point, then check valve #2 tightness against backpressure.

An RP has four test cocks: upstream of check #1, in the zone before the relief valve, in the zone before check #2, and downstream of check #2.

Intermittent discharge often points to supply pressure fluctuations. Continuous discharge is more likely to indicate fouling, leakage, or a failed component.

A double check valve assembly has two independently acting check valves, shutoff valves, and test cocks. It is used for non-health hazards and does not provide visible failure warning.

Local practice content uses 1.0 psid as the minimum differential pressure each DC check valve must hold during the field test.

A DC can fail without visible discharge and relies on check-valve integrity alone. Health-hazard conditions require an RP or air gap when backpressure can occur.

A pressure vacuum breaker has a loaded check valve and an air inlet valve. It protects against backsiphonage only, not backpressure.

Local practice content uses 12 inches above downstream piping and the highest point of use as the minimum PVB installation height.

Backpressure can hold the air inlet closed and force the check valve open. Vacuum breakers depend on pressure dropping enough to admit air.

A spill-resistant vacuum breaker is similar to a PVB but designed to reduce water spillage from the air inlet. It still protects against backsiphonage only.

An AVB protects against backsiphonage only and cannot be under continuous pressure or have downstream shutoff valves. It is not a testable assembly like a PVB.

Detector assemblies include a bypass meter to detect unauthorized or unintended flow, commonly on fire sprinkler connections.

Use an air gap or RP assembly for contaminant health hazards where backpressure may occur. A PVB protects only against backsiphonage.

A DC assembly may be acceptable for non-health hazard backpressure conditions when allowed by the authority having jurisdiction.

Before testing, record assembly type, size, manufacturer, model, serial number, location, and direction of flow. Verify shutoffs and obvious installation problems.

Connect hoses, slowly open test cocks, and bleed air from the hoses. Air in the test kit can create inaccurate differential readings.

A differential gauge measures pressure difference between two points. Backflow testing depends on reading small psid values accurately.

Test gauges must be calibrated on the required schedule for the certifying program or jurisdiction. Local metadata notes calibration within the last 12 months for exam performance equipment.

Both test kits route high, low, and bypass connections to measure differentials. Know your kit's valve positions before the performance exam.

Open shutoff valves slowly when returning an assembly to service. Sudden flow changes can create pressure surges that damage piping or assemblies.

Record actual failed readings, notify the required parties, and recommend repair. A failed assembly must be repaired and retested before it is accepted.

Sand, scale, or debris on a resilient seat can stop a check valve from sealing. This is a common cause of low psid readings and field-test failure.

A leaking shutoff can interfere with test results by allowing pressure or flow where the procedure assumes isolation. Identify and document the issue.

A leaking RP second check under backpressure can raise zone pressure and cause relief-valve discharge.

Water flowing from a PVB air inlet while the assembly is pressurized indicates an air-inlet valve problem that requires repair.

An assembly must be accessible, oriented correctly, protected from flooding or freezing as required, and installed with adequate clearance for testing and repair.

A horizontal RP should have the relief valve pointing downward with discharge clearance so water can escape freely if the relief valve opens.

A complete report identifies the assembly and location, records test readings, pass/fail status, repairs if known, tester information, and date.

Many programs require periodic testing, often annually, but exact frequency is set by the authority having jurisdiction and the hazard level.

A cross-connection survey identifies hazards, evaluates degree of hazard, and determines whether containment, isolation, or both are required.

A testable assembly has shutoff valves and test cocks for field verification. Some devices, such as AVBs, provide protection but are not field-tested the same way.