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BLD-PLUM06-08 · Lesson 8 · 16 clock hours · practice

Calibrated Test Kit Operation and Field Test Procedures: DCVA

Objective. The learner performs a complete ASSE field test on a double-check valve assembly using a calibrated differential-pressure gauge test kit, records all readings on a standard field test report form, and correctly interprets pass or fail.

Why the DCVA Test Matters

A double-check valve assembly (DCVA) protects potable water supplies from back-siphonage and backpressure by using two independently acting spring-loaded check valves in series. When either check fails to hold, contaminated water can reverse into the distribution system. Field testing with a calibrated differential-pressure gauge kit verifies that each check valve creates enough resistance to stop reverse flow. This test is required at installation, after repair, and on a regular schedule set by the authority having jurisdiction (AHJ). The ASSE field test procedures govern how the test is performed, and the ASSE standard field test report form documents every reading.

Safety Before You Touch Anything

Before attaching the test kit, address these hazards:

Test Kit Components

A standard differential-pressure gauge field test kit contains:

Before attaching hoses to any assembly, zero-set the gauge with both needle valves open and the bleed valve open until the needle reads exactly zero, then close the bleed valve. Flush each hose by opening the test cock briefly to purge air bubbles; air in the hose causes erratic readings.

DCVA Anatomy and Test Cock Identification

A DCVA has four test cocks labeled TC1 through TC4 (some manufacturers use different labels; verify with the manufacturer's plate):

Test cocks are opened with a flat-blade screwdriver or a test cock key; one-quarter turn opens them.

Field Test Sequence: Check No. 2 First

ASSE procedure tests Check No. 2 before Check No. 1 to avoid artificially loading the first check during the second check test.

Step 1 — Record assembly information. Serial number, make, model, size, location, date, and tester name go on the form before any test step.

Step 2 — Observe and record system pressure. Attach the high-side hose to TC1, open the needle valve, and read line pressure. Record it.

Step 3 — Test Check No. 2. Connect the high-side hose to TC2 and the low-side hose to TC3. Close SV2 (downstream shutoff). Slowly open both needle valves. Bleed air from hoses, then re-zero. Slowly open TC3 to bleed down the low side, reducing pressure downstream of Check No. 2. The differential pressure reading shows how much Check No. 2 is holding. Record the reading when the gauge stabilizes.

Acceptance criterion for Check No. 2: The differential pressure must be 1.0 psi or greater (some AHJs require the manufacturer's specified minimum; always apply the more stringent value).

Step 4 — Test Check No. 1. With SV2 still closed, move the low-side hose from TC3 to TC2, and keep the high-side hose on TC1. Bleed and re-zero. Slowly bleed down TC2 to reduce pressure in the zone. The gauge shows how much Check No. 1 is holding. Record the reading when stable.

Acceptance criterion for Check No. 1: The differential pressure must be 1.0 psi or greater.

Step 5 — Restore the assembly. Close all test cocks, remove hoses, open SV2, and verify normal flow is restored.

Step 6 — Complete the report form. Record every reading, the pass/fail determination for each check, and your signature. Leave no required field blank.

Interpreting Results

| Reading | Determination |

|---|---|

| ≥ 1.0 psi on both checks | PASS — assembly is functioning |

| < 1.0 psi on either check | FAIL — assembly must be repaired or replaced before returning to service |

A failed assembly must be reported to the AHJ per local requirements. Do not return the assembly to service without authorization.

Gauge Care After the Test

Drain hoses completely, coil without kinking, and store the kit in its case. Log the test kit serial number and calibration expiration date on every report form you submit.

Key terms9

Double-check valve assembly (DCVA)A backflow preventer containing two independently acting spring-loaded check valves in series, used to protect against backpressure and back-siphonage in low-to-moderate hazard applications.
Differential pressureThe difference in pressure measured between two points in a system; the value the test kit gauge displays when checking how much resistance a check valve creates.
Test cockA small quarter-turn valve built into the DCVA body that provides a port for connecting field test kit hoses; labeled TC1 through TC4.
Calibrated test kitA differential-pressure gauge and associated hoses, needle valves, and bleed valves whose accuracy has been verified against a traceable standard within the required calibration interval.
Zero-settingThe procedure of bleeding the gauge body with both needle valves open until the needle reads exactly zero before attaching hoses to the assembly, ensuring accurate differential readings.
Acceptance criterionThe minimum differential-pressure value a check valve must hold to pass the field test; for a DCVA, each check must hold 1.0 psi or greater under standard ASSE procedure.
Authority having jurisdiction (AHJ)The organization, office, or individual responsible for enforcing requirements, in this context the entity that mandates testing schedules and receives completed field test report forms.
Back-siphonageReverse flow caused by negative pressure (partial vacuum) in the supply main, which can draw contaminants from a connected system into the potable water supply.
Bleed valveA valve on the test kit gauge body used to release trapped water and return the needle to zero between measurements.

Worked examples4

1. During a Check No. 2 test, the high-side hose reads 52.0 psi (connected to TC2) and the low-side hose reads 50.8 psi (connected to TC3) when the gauge stabilizes. What is the differential pressure, and does Check No. 2 pass or fail?
  1. Identify the high-side pressure: 52.0 psi (TC2).
  2. Identify the low-side pressure: 50.8 psi (TC3).
  3. Calculate differential pressure: 52.0 psi − 50.8 psi = 1.2 psi.
  4. Compare to acceptance criterion: 1.2 psi ≥ 1.0 psi.
Answer: Differential pressure = 1.2 psi. Check No. 2 PASSES.
2. During a Check No. 1 test, the high-side hose reads 53.4 psi (TC1) and the low-side hose reads 52.7 psi (TC2) when stable. Does Check No. 1 pass or fail?
  1. Identify the high-side pressure: 53.4 psi (TC1).
  2. Identify the low-side pressure: 52.7 psi (TC2).
  3. Calculate differential pressure: 53.4 psi − 52.7 psi = 0.7 psi.
  4. Compare to acceptance criterion: 0.7 psi < 1.0 psi.
Answer: Differential pressure = 0.7 psi. Check No. 1 FAILS. The assembly must be taken out of service, repaired or replaced, and retested before returning to service.
3. A tester forgets to zero-set the gauge before the test. The gauge reads +0.4 psi with the bleed valve open and no hoses attached. After connecting to the assembly, the gauge reads 1.3 psi for Check No. 2. What is the corrected differential pressure, and what should the tester do?
  1. Identify the gauge offset (error): the needle reads +0.4 psi at zero condition, meaning every reading is inflated by 0.4 psi.
  2. Corrected differential pressure: 1.3 psi − 0.4 psi = 0.9 psi.
  3. Compare corrected value to acceptance criterion: 0.9 psi < 1.0 psi.
  4. Determine action: the reading is invalid because the gauge was not zeroed. The tester must zero-set the gauge, flush the hoses, and repeat the test from the beginning with valid, corrected readings before making a pass/fail determination.
Answer: Corrected differential = 0.9 psi, which would be a FAIL — but more importantly, the entire test is invalid and must be repeated after properly zeroing the gauge.
4. Check No. 2 shows a differential pressure of exactly 1.0 psi and Check No. 1 shows 1.5 psi. What is the overall assembly determination?
  1. Check No. 2 differential: 1.0 psi. Acceptance criterion: ≥ 1.0 psi. Result: PASS (1.0 psi meets the criterion).
  2. Check No. 1 differential: 1.5 psi. Acceptance criterion: ≥ 1.0 psi. Result: PASS.
  3. Both checks pass, so the overall assembly determination is PASS.
Answer: Both checks pass. Overall assembly determination: PASS. Record 1.0 psi for Check No. 2 and 1.5 psi for Check No. 1 on the field test report form.
In class: Instructor demonstration of test kit components: needle valves, hoses, gauge, bleed valves; learners identify each part and practice zero-setting and flushing the hoses before attachment · Step-by-step guided practice: instructor calls each test step aloud while learners perform the DCVA test sequence (check No. 2 first, then check No. 1) on training-rig assemblies set to known conditions · Independent test: each learner performs a solo DCVA field test, records all differential pressure readings on the ASSE form, and states the pass/fail determination with the applicable acceptance criterion
Materials: Calibrated differential-pressure gauge field test kits (one per learner or per pair); DCVA assemblies on training rigs set to pass and fail conditions; ASSE 5013 field test procedure; ASSE standard field test report forms; stopwatch
Check: Independent test: all test steps performed in correct sequence; readings recorded accurately (instructor verifies against known rig settings); pass/fail determination correct; completed form has no blank required fields—80% procedural accuracy minimum

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

ASSE Backflow field test procedures
1. When performing a DCVA field test, which check valve is tested FIRST and why?
ASSE Backflow field test procedures
2. What is the minimum differential pressure each check valve in a DCVA must hold to receive a passing result under standard ASSE field test criteria?
ASSE Backflow field test procedures
3. A tester connects the high-side hose to TC2 and the low-side hose to TC3, closes SV2, and observes the gauge. This configuration tests which component?
ASSE Backflow field test procedures
4. Before attaching test kit hoses to the assembly, the tester should:
ASSE Backflow field test procedures
5. A DCVA field test shows Check No. 1 differential = 1.8 psi and Check No. 2 differential = 0.6 psi. The correct determination is:
Safety — PPE and hazard control
6. Which personal protective equipment item is most critical when opening test cocks on a pressurized DCVA?
ASSE Backflow — test equipment and calibration
7. A tester's differential-pressure gauge kit shows a calibration sticker expired three months ago. The correct action is to:
ASSE Backflow — documentation and reporting
8. After completing a DCVA field test and recording all readings, which required field test report form fields must NOT be left blank to satisfy ASSE documentation requirements?
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