Failed Second Check on a Double-Check Assembly: Repair or Replace?
A tester is performing the annual test of a 2-inch double-check valve assembly at a car wash. The assembly is 14 years old and has been repaired twice in the past four years. During the test, the first check holds 1.5 psi, but the second check will not hold any pressure and the gauge drops to zero immediately. The tester removes the second check and finds a heavily pitted seat and a torn disc. Replacement parts are available, but the local code requires that a double-check assembly be replaced if it fails two consecutive annual tests. The owner wants the cheapest option and asks the tester to simply clean the seat and reuse the old disc.
1. Should the tester clean the seat and reuse the old disc to save money? Explain the technical and code considerations.
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No. A pitted seat and a torn disc cannot be restored by cleaning. The torn disc will not seal against the seat, and the pitting will prevent a reliable seal even with a new disc unless the seat is resurfaced or replaced. Reusing the old disc would produce a false passing result and would leave the assembly unable to protect the water supply. The tester should replace the seat and disc with manufacturer-approved parts, or replace the entire assembly if the seat cannot be resurfaced. The local code requirement that a double-check assembly be replaced after two consecutive annual test failures also applies here, and the tester must follow it. The tester should document the condition of the seat and disc, the repair or replacement performed, and the final test results.
2. After the repair, the first check holds 1.8 psi and the second check holds 1.1 psi. The owner asks whether the assembly can be returned to service. What should the tester say, and what documentation is required?
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The assembly can be returned to service because both checks meet the minimum differential requirements for a double-check assembly, which are typically 1.0 psi or greater for each check. The tester should record the first-check reading of 1.8 psi and the second-check reading of 1.1 psi, along with the repair performed, the parts used, and the date. The report should state that the assembly passed after repair and that the full test sequence was repeated. The tester should also note the assembly's age and repair history, and advise the owner that the assembly has now failed two consecutive annual tests if the prior failure is documented, which may trigger the local replacement requirement. The owner should be informed in writing of the code requirement and the need to plan for replacement.