Question 1

What does PSID stand for in backflow pressure testing?

Accepted Answer

PSID (Pounds Per Square Inch Differential) measures the pressure difference across a check valve. It indicates how much force is pushing the valve closed and is critical for determining if a device passes testing.

Question 2

What is the minimum PSID required for Check #1 in a Double Check assembly?

Accepted Answer

Double Check assemblies require Check #1 to maintain a minimum of 1.0 PSID closure pressure. This ensures the valve is positively sealed and protecting against backflow.

Question 3

What is the minimum PSID required for Check #2 in a Double Check assembly?

Accepted Answer

Check #2 in a Double Check assembly must also maintain at least 1.0 PSID closure pressure to prevent backflow through the assembly.

Question 4

What is the minimum PSID for Check #1 in a Reduced Pressure Principle device?

Accepted Answer

RPZ devices require higher closure pressures than Double Check assemblies. Check #1 must maintain at least 5.0 PSID to ensure reliable protection in high hazard applications.

Question 5

What is the minimum PSID for the relief valve in a Reduced Pressure Principle device?

Accepted Answer

The relief valve in an RPZ device must open when zone pressure exceeds downstream pressure by 2.0 PSID or more, preventing excessive pressure buildup between the check valves.

Question 6

What is the minimum PSID for the check valve in a Pressure Vacuum Breaker?

Accepted Answer

PVB check valves require a minimum 1.0 PSID closure pressure to prevent backflow through the device during backsiphonage conditions.

Question 7

What is the minimum PSID for the air inlet valve in a Pressure Vacuum Breaker?

Accepted Answer

The air inlet valve in a PVB must also maintain at least 1.0 PSID closure pressure to prevent air from leaking when supply pressure is present.

Question 8

A test shows Check #1 reading 0.8 PSID. Does this pass testing for a Double Check assembly?

Accepted Answer

0.8 PSID is below the required 1.0 PSID minimum for a Double Check assembly check valve. Even considering ±0.2 PSID gauge accuracy, this reading indicates failure and the device requires repair.

Question 9

A test shows Check #1 on an RPZ reading 5.2 PSID. Does this pass testing?

Accepted Answer

5.2 PSID exceeds the required 5.0 PSID minimum for RPZ Check #1, indicating the valve is functioning properly and providing adequate closure pressure.

Question 10

What does a PSID reading of 0.0 indicate?

Accepted Answer

A 0.0 PSID reading means there is no pressure differential to keep the check valve closed. The valve is fully open or non-functional, failing to provide any backflow protection.

Question 11

The relief valve on an RPZ is continuously discharging water. What does this indicate?

Accepted Answer

Continuous relief discharge indicates Check #1 is allowing water into the zone between the checks. The pressure buildup triggers the relief valve, indicating Check #1 failure and device malfunction.

Question 12

What is the acceptable accuracy range for a backflow test gauge?

Accepted Answer

Test gauges must be accurate to within ±0.2 PSID and must be calibrated annually to ensure testing accuracy and reliability of results.

Question 13

A reading is 1.1 PSID with a gauge accuracy of ±0.2 PSID. What is the worst-case actual pressure?

Accepted Answer

With a reading of 1.1 PSID and ±0.2 PSID accuracy, the worst case is 1.1 - 0.2 = 0.9 PSID. This is below the 1.0 PSID minimum and would likely fail for a Double Check assembly.

Question 14

When testing an RPZ device, why must Check #1 reading be greater than Check #2 reading?

Accepted Answer

Check #1 is upstream and receives full supply pressure, so its reading should exceed Check #2's reading. If readings are equal or reversed, it indicates a check valve malfunction.

Question 15

Test results show: Check #1 = 2.0 PSID, Check #2 = 3.0 PSID on a Double Check assembly. What does this indicate?

Accepted Answer

Check #2 downstream should always read lower than Check #1 upstream. A higher Check #2 reading indicates a testing error, improper gauge connection, or severe device malfunction.

Question 16

What effect does increasing supply pressure have on backflow prevention device test readings?

Accepted Answer

Higher supply pressure increases the pressure differential across check valves, resulting in higher PSID readings. This is why consistent supply pressure is important during testing.

Question 17

During testing, the pressure gauge needles fluctuate significantly. What should the technician do?

Accepted Answer

Pressure fluctuations are normal as the system stabilizes. The technician should wait for readings to stabilize before recording final test values. Fluctuations may indicate air in hoses or transient pressure changes.

Question 18

Why is it important to bleed air from test gauge hoses before recording test results?

Accepted Answer

Air pockets in hoses compress and expand, causing gauge readings to fluctuate and be inaccurate. Bleeding air ensures the gauge directly measures actual line pressure.

Question 19

Test cocks are numbered in sequence on a backflow device. What is the purpose of test cock #1?

Accepted Answer

Test cock #1 is the upstream connection, allowing measurement of supply pressure entering the device. This baseline is used to calculate differential pressure across each check.

Question 20

What is the purpose of test cock #3 on an RPZ device?

Accepted Answer

Test cock #3 connects to the zone between Check #1 and Check #2 (and the relief valve). It allows measurement of zone pressure to verify relief valve operation.

Question 21

A Double Check assembly shows: Check #1 = 1.2 PSID, Check #2 = 1.1 PSID. Does this device pass?

Accepted Answer

Both readings exceed 1.0 PSID minimum, indicating both check valves are functioning with adequate closure pressure. This device passes the pressure test.

Question 22

An RPZ device shows: Check #1 = 4.8 PSID. Does this pass the minimum requirement?

Accepted Answer

4.8 PSID is below the required 5.0 PSID minimum for an RPZ Check #1, even accounting for ±0.2 PSID gauge accuracy. This indicates Check #1 failure and device repair is needed.

Question 23

What does differential pressure measure in a backflow prevention device?

Accepted Answer

Differential pressure (PSID) measures the pressure difference between upstream and downstream of a check valve. Higher differential means stronger closure force and better protection.

Question 24

Temperature changes in a water system can affect pressure readings. How?

Accepted Answer

As water temperature increases, it expands. In closed systems or with backflow prevention devices, this thermal expansion increases pressure readings. Temperature-related changes must be considered in testing.

Question 25

An RPZ relief valve is set to open at 2.0 PSID differential. What does this mean?

Accepted Answer

The relief valve opens when zone pressure (between the checks) exceeds downstream pressure by 2.0 PSID, preventing excessive pressure buildup and protecting the downstream check valve.

Question 26

What is the relationship between static pressure and differential pressure in testing?

Accepted Answer

Static pressure is the absolute pressure in a line, while differential pressure is the pressure drop across a component. Both are important in backflow device testing and evaluation.

Question 27

Test readings on a Double Check show readings that barely meet minimum (exactly 1.0 PSID). Why might this be concerning?

Accepted Answer

Readings at the absolute minimum provide no safety margin. With ±0.2 PSID gauge accuracy, the actual reading could be 0.8 PSID (failing). Best practice favors readings with comfortable safety margin above minimums.

Question 28

When operating high/low side needle valves during testing, what is their primary function?

Accepted Answer

High and low side needle valves control the rate of pressure increase into the gauge, allowing technicians to safely bring gauges to accurate readings without spiking needles or damaging sensitive equipment.

Question 29

An RPZ device shows: Check #1 = 6.0 PSID, Check #2 = 3.0 PSID, Relief zone = 4.0 PSID. What does this indicate?

Accepted Answer

With Check #2 at 3.0 PSID (downstream), zone pressure of 4.0 PSID exceeds it by more than the 2.0 PSID relief setting, indicating the relief valve is not opening and likely fouled or broken.

Question 30

Why should test gauge hoses be disconnected immediately after testing is complete?

Accepted Answer

Leaving pressurized hoses connected stresses gauge seals and internal components, reducing accuracy and lifespan. Disconnecting immediately after testing preserves gauge calibration.

Question 31

A PVB device shows Check = 1.0 PSID and Air Inlet = 0.9 PSID. What is the status?

Accepted Answer

The air inlet reading of 0.9 PSID is below the required 1.0 PSID minimum. Even with ±0.2 PSID accuracy, this suggests air inlet valve failure and device malfunction.

Question 32

If supply pressure is unusually low during testing, what impact does this have on check valve readings?

Accepted Answer

Lower supply pressure reduces the differential pressure across check valves, resulting in lower PSID readings. This may cause devices to fail if readings drop below minimums.

Question 33

Test results are borderline passing with readings near the minimum. What is the appropriate recommendation?

Accepted Answer

While borderline passing readings meet current requirements, they indicate the check valves are worn and may fail soon. Repair scheduling is appropriate to maintain safety margin.

Question 34

What condition causes the gauge to read lower than expected on all test cocks?

Accepted Answer

Lower than expected readings across all points could result from air in hoses, low supply pressure, or valve failures. The technician should troubleshoot each possibility systematically.

Question 35

After repair work, test results show Check #1 reading exactly at the previously failed value. What might this indicate?

Accepted Answer

If a repaired component returns to the same failing reading, the repair may have been ineffective or incomplete. The underlying cause (worn disc, broken spring, debris) may not have been properly addressed.

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