BAT Backflow Assembly Tester Maintenance & Repair Techniques 3 — Questions and Answers
Question 1: Which condition would require a backflow assembly to be taken out of service and replaced rather than repaired?
- A worn O-ring on a test cock fitting
- A cracked body casting or body that cannot hold pressure (Correct answer)
- A stiff but functional isolation valve handle
- A slightly corroded test cock nipple
Correct answer: A cracked body casting or body that cannot hold pressure
A cracked body or one unable to hold rated pressure is a structural failure that cannot be safely repaired in the field and requires full replacement.
Question 2: A pressure vacuum breaker (PVB) air inlet valve fails to open during testing. After cleaning, it still fails. What is the next corrective step?
- Increase upstream pressure to force the valve open
- Replace the air inlet valve assembly (Correct answer)
- Tape the air inlet closed and retest
- Adjust the tension on the air inlet spring by bending the retaining clip
Correct answer: Replace the air inlet valve assembly
If cleaning does not restore air inlet valve function, the assembly must be replaced since a non-operating air inlet means the PVB cannot provide backflow protection.
Question 3: During maintenance of a spill-resistant pressure vacuum breaker (SRPVB), the tester finds the check valve will not seat. After replacing the check disc, the problem persists. What should be inspected next?
- The upstream isolation valve packing
- The check valve seat for scoring, pitting, or debris (Correct answer)
- The downstream piping for leaks
- The air inlet canopy for debris
Correct answer: The check valve seat for scoring, pitting, or debris
If a new disc still does not seat properly, the seat itself must be inspected for scoring, pitting, or embedded debris that prevents a complete seal.
Question 4: What is the maximum allowable test cock leakage when performing a tightness check after reassembly of a backflow preventer?
- Any drip rate under 10 drops per minute is acceptable
- Test cocks must be completely drip-free (zero leakage) (Correct answer)
- One drip per second is the standard allowance
- Up to 0.5 gallons per hour is permitted
Correct answer: Test cocks must be completely drip-free (zero leakage)
Test cocks must be completely drip-free after assembly, as any leakage indicates improper seating of the test cock plug or a damaged valve seat.
Question 5: A tester notices heavy scale buildup inside the body of a double check detector assembly (DCDA) during maintenance. What is the recommended cleaning method?
- High-pressure steam injection
- Mechanical brushing with a nylon brush and flushing with clean water (Correct answer)
- Muriatic acid soak for 30 minutes
- Wire brushing with a steel brush
Correct answer: Mechanical brushing with a nylon brush and flushing with clean water
Nylon brushing followed by clean water flushing removes scale without damaging internal surfaces or leaving chemical residues that could affect potable water quality.
Question 6: After replacing all internal components of an RPZA, the tester pressurizes the assembly and hears water flowing out of the relief valve port. What is the most likely cause?
- The upstream isolation valve is fully open
- Check valve #2 (downstream) is not seating properly (Correct answer)
- The inlet strainer is clogged
- The test cock on the zone is open
Correct answer: Check valve #2 (downstream) is not seating properly
If the zone pressure drops below relief valve opening threshold due to a leaking downstream check, the relief valve will discharge; a leaking #2 check is the most common cause.
Question 7: Which material is approved for lubricating the packing of an isolation valve on a potable water backflow assembly?
- WD-40 or equivalent penetrating oil
- NSF 61 certified, food-grade lubricant or silicone grease (Correct answer)
- Standard pipe thread compound
- Automotive grease
Correct answer: NSF 61 certified, food-grade lubricant or silicone grease
Only NSF 61 certified, food-grade lubricants are approved for use on components contacting potable water to prevent contamination.
BAT Backflow Assembly Tester Maintenance & Repair Techniques 3
Which condition would require a backflow assembly to be taken out of service and replaced rather than repaired?