The double check valve assembly test sheet

A double check valve assembly is two independently loaded check valves in series between two resilient-seated shutoff valves, with test cocks. There is no relief valve, so the test is a direct measurement of each check's ability to hold a differential in the direction of flow. A complete sheet carries four blocks.

• Facility and service — customer, service address, contact, water purveyor, meter or account number, assembly location, test date and test type. On fire services, note the service type explicitly; it changes who else wants a copy.
• Assembly identification — DC, DCVA or DCDA, manufacturer, model, serial, size, and hazard classification of the service being protected.
• Readings — check valve #1 differential, check valve #2 differential, shutoff #1 and #2 tightness, static line pressure. On a DCDA, the bypass assembly readings as well.
• Tester, gauge and signatures — certification number and expiry, company and license, gauge make, model, serial and calibration date, signatures.

These are the thresholds BackflowPass applies to the double check family, read out of its rule engine. DCDA inherits them; the bypass assembly is graded on its own readings.

Both checks must pass. A missing reading is reported as incomplete rather than as a failure, and the overall result is derived from the readings rather than selected by the tester. Put your own numbers through it on the pass/fail calculator.

Follow the procedure your certification and purveyor require; the sequence below is the ordinary shape of a differential gauge test on a double check, given so you know which blank gets filled when.

1. 1

   Identify, inspect, record line pressure

   Read the tag for type, make, model, serial and size. Note the installation and record static supply pressure.

2. 2

   Flush the test cocks

   Clear debris before the gauge is attached, so grit does not end up under a check you are about to grade.

3. 3

   Test check valve #1

   Measure the differential across the first check with the gauge bled and the reading settled. Baseline pass is 1.0 PSID or greater, held steady rather than falling.

4. 4

   Test check valve #2

   Repeat for the second check. Baseline pass is 1.0 PSID or greater. Record both values even when the first one already failed — the repair depends on knowing.

5. 5

   Verify both shutoff valves

   Record each as tight or leaked. A leaking downstream shutoff undermines the differentials you just took through it.

6. 6

   Restore service and sign

   Close test cocks, restore the service, confirm normal operation, then sign with certification and gauge calibration details on the sheet.

A double check detector assembly is the same double check body with a metered bypass around it. The bypass exists so that a small continuous flow — a leak, or water taken from a fire service without authorisation — registers on a meter instead of passing unseen through the main line.

Extra fields the sheet needs

• Bypass meter make, model and serial, plus the reading if your program collects it.
• Bypass assembly identification — it is a small assembly in its own right and is tested as one.
• The bypass assembly's own check differentials, graded against the same double check minimums.
• Confirmation that the bypass was returned to service, valves open, after testing.

Practical cautions on fire services

• Fire protection water is life safety: coordinate the shutdown, and confirm who must be notified before you close a valve.
• Note the service type as fire protection on the report — the fire marshal or insurer may want the same document the purveyor gets.
• An RPDA is the reduced pressure equivalent of the same idea, and is tested on the RP rule family instead. See the RP/RPZ reference for those readings.

Double check failures are usually mechanical and usually cheap; what makes them expensive is a sheet that does not say what was wrong.

• Check below minimum — debris on the seat, worn or nicked rubber, or a weak spring. Clean first and re-measure; a sizeable number of "failed" checks are a grain of pipe scale.
• Both checks low — look for a systemic cause: recent main work upstream, sediment, or a body that has been in service a very long time.
• Shutoff leaks — repair or replace, then retest both checks from the start rather than reusing the earlier numbers.
• No differential at all — verify the gauge and hose connections and that the correct test cocks are open before condemning the assembly.

The report keeps the failed initial readings, the repair actions, and the full final retest. A passing retest reports as passed after repair; a retest with a missing reading stays incomplete instead of reporting a pass.

Work down the fields above on paper, or open the generator, choose DC, DCVA or DCDA, and the form will show only the readings the double check family uses. Every differential is graded as you type, both shutoffs are explicit toggles rather than assumptions, and the finished test report exports as a single 8.5×11 page.

• No account and no signal required — the calculation engine and the PDF are on the device.
• Saved customers and assemblies mean next year's annual starts from last year's identity fields with blank readings.
• Switching from a DC to an RP mid-form warns you before it clears readings that do not carry over.
• Pro and Fleet plans put your company logo and details on the report in place of the BackflowPass footer.