BAT Backflow Assembly Tester Maintenance & Repair Techniques 2 — Questions and Answers
Question 1: When disassembling a reduced pressure zone (RPZ) assembly for maintenance, what is the correct first step?
- Shut off downstream isolation valve only
- Relieve pressure by opening test cocks before closing isolation valves
- Remove the relief valve before closing any valves
- Close both isolation valves simultaneously before opening any test cocks (Correct answer)
Correct answer: Close both isolation valves simultaneously before opening any test cocks
Both isolation valves must be closed simultaneously (or upstream first, then downstream) before opening test cocks to safely depressurize the assembly.
Question 2: A check valve disc in an RPZA is found to have a small chip on the seating surface. What is the appropriate repair action?
- Sand the chip smooth with fine-grit sandpaper
- Replace the disc and seat as a matched set (Correct answer)
- Apply epoxy sealant to fill the chip
- Continue service if the chip is less than 1mm
Correct answer: Replace the disc and seat as a matched set
Chipped or damaged disc and seat surfaces must be replaced as a matched set to ensure a proper, leak-free seal.
Question 3: Which tool is specifically required to properly compress and reinstall a check valve spring during RPZA repair?
- Standard slip-joint pliers
- A spring compression tool or assembly jig appropriate for the device (Correct answer)
- Needle-nose pliers
- A rubber mallet
Correct answer: A spring compression tool or assembly jig appropriate for the device
A proper spring compression tool or manufacturer-specific jig is required to safely compress and seat springs without damaging components.
Question 4: After repairing a double check valve assembly (DCVA), the tester observes that check valve #1 opens at 0.5 psi during testing. What does this indicate?
- The check valve is functioning correctly
- The check valve spring is too weak or the disc is sticking open (Correct answer)
- The check valve spring is too strong
- The downstream pressure is too high
Correct answer: The check valve spring is too weak or the disc is sticking open
A properly functioning DCVA check valve should open against at least 1.0 psi of differential pressure; opening at 0.5 psi indicates a weak spring or sticking disc.
Question 5: What is the purpose of applying a thin coat of silicone grease to O-rings during RPZA maintenance?
- To chemically bond the O-ring to the seat
- To lubricate for easy installation and prevent tearing during assembly (Correct answer)
- To increase the O-ring's chemical resistance
- To permanently seal small nicks in the O-ring
Correct answer: To lubricate for easy installation and prevent tearing during assembly
Silicone grease lubricates O-rings to ease installation and prevent tearing or rolling during assembly without degrading the elastomer.
Question 6: A tester replaces the relief valve seat in an RPZ assembly. After reassembly and testing, the relief valve still drips. What is the most likely cause?
- The upstream isolation valve is partially closed
- Debris is present between the new seat and disc, or the disc is damaged (Correct answer)
- The zone differential is too high
- The downstream check valve is too strong
Correct answer: Debris is present between the new seat and disc, or the disc is damaged
Residual debris on mating surfaces or a damaged disc is the most common cause of continued relief valve dripping after seat replacement.
Question 7: When reassembling an RPZA after repair, in what order should major internal components typically be reinstalled?
- Relief valve first, then check valve #2, then check valve #1
- Check valve #1 (upstream), then check valve #2, then relief valve (Correct answer)
- Relief valve first, then check valve #1, then check valve #2
- Order does not matter if all components are installed before closing the body
Correct answer: Check valve #1 (upstream), then check valve #2, then relief valve
Standard practice is to install the upstream check valve (#1) first, followed by check valve #2, and then the relief valve to allow proper seating and alignment.
BAT Backflow Assembly Tester Maintenance & Repair Techniques 2
When disassembling a reduced pressure zone (RPZ) assembly for maintenance, what is the correct first step?