8.1 RP Field Test Procedure (USC 10th Edition)

8.1 RP Field Test Procedure (USC 10th Edition)

Quick Answer: Under USC 10th Edition practice, an RP (ASSE 1013) field test typically obtains the relief valve opening point first (≥ 2.0 psid), then tests check #2 for tightness against backpressure (tight or leaked — no psid value), then measures check #1 static differential (≥ 5.0 psid and above the relief opening point). Pre-test: notify, inspect, identify TC1–TC4, and use shutoffs deliberately. Finish by restoring shutoffs and removing the kit safely. Some ASSE-recognized school sequences test relief last—follow your approved procedure on the practical while mastering USC 10th for the written exam.

Why sequence matters

Field testing is not “attach hoses and hope for three numbers.” Each step places the assembly and gauge in a defined hydraulic condition so a single reading answers a single question:

If you scramble the order without understanding why, you can contaminate a reading with residual pressure, open the wrong test cock, or “pass” an assembly that would fail under the standard sequence. The practical exam grades procedure as well as final numbers.

Procedure note for candidates: Your ASSE-recognized course may teach a field procedure that tests the relief last. That can still be an approved path. This guide emphasizes USC 10th as a widely used reference and one ASSE-recognized option. Memorize the pass criteria either way; practice the exact hookup and valve choreography your school requires for the hands-on exam.

Pre-test: notify, inspect, identify, plan shutoffs

Before any hose touches a test cock:

1. Notify the owner/operator and, where required by the purveyor or AHJ, the water supplier. Confirm it is acceptable to close shutoff #2 (and, when needed, shutoff #1) and that critical processes can tolerate a brief interruption or static test window.
2. Visual inspection — orientation correct, clearance and relief discharge path acceptable, no missing test cocks or damaged shutoffs, no continuous relief dump before you start (note it if present), freeze protection and air-gap/drain arrangements intact. Document obvious defects before testing so you do not “create” a failure by ignoring a broken test cock.
3. Identify TC1–TC4 on this manufacturer’s body. The published USC, ASSE, and NEWWA procedures all put the high hose on TC2 and the low hose on TC3, which tells you the standard topology:

Memorize it as “2 is supply, 3 is the zone, 4 is downstream.” Always verify against the manufacturer’s diagram—do not assume every casting looks the same—but if a body’s numbering does not produce a positive differential with high on TC2 and low on TC3, stop and re-identify before you record anything. 4. Shutoff plan — know which shutoff you will close for each step. USC-style work commonly uses shutoff #2 closed for static and backpressure conditions, with shutoff #1 left open to maintain supply reference unless a specific step requires otherwise. Never force a seized shutoff; report it.

Bleed and hookup discipline (Chapter 7) applies: fill and purge air from hoses and the gauge so differentials are real, not trapped air artifacts.

Establish connections (conceptual USC 10th-style pattern)

With a differential pressure gauge (three- or five-valve style per your training):

• Connect the high side to the higher-pressure location required for the step (TC2, the inlet body, for relief and check #1 work).
• Connect the low side to the lower-pressure location (TC3, the zone, for relief and check #1 work), and run the bypass hose to TC4 when the step needs backpressure on check #2.
• Open test cocks only as needed; keep unused cocks closed.
• Establish a stable static or controlled condition before recording.

Exact hose-to-test-cock maps differ slightly by gauge type and school worksheet. What does not change is the physics of each test.

Test 1 — Relief valve opening point (first in typical USC order)

Goal: Find the inlet-to-zone differential at which the differential pressure relief valve opens.

Meaning of the reading: As you carefully reduce the apparent differential (by the approved method of introducing zone pressure rise or controlled bleeding per your manual), watch for the relief to open or spit. The gauge reading at that moment is the opening point in psid.

Pass idea: Opening point ≥ 2.0 psid. A relief that opens at 1.2 psid fails—the buffer between normal closed operation and dump is too small. A relief that never opens when it should also fails (stuck closed is a different and serious failure mode).

Record the exact opening value (for example, 2.4 psid). You will need it later: check #1 must sit above this number, not merely above an abstract 5.0.

Test 2 — Check #2 tightness against backpressure

Goal: Prove check #2 is tight in the reverse direction—the direction that matters when customer-side pressure tries to push back into the zone.

Meaning of the reading: Supply pressure is routed through the bypass hose to test cock #4 so backpressure is applied downstream of check #2. The psid on the gauge may or may not decrease. If the relief valve stays closed and the gauge stabilizes above the relief valve opening point, check #2 is seating and you record it as tight. If the differential collapses to the relief opening point and the relief discharges, #2 is leaking in reverse.

Pass idea: Check #2 is tight against backpressure — a yes/no result, not a number. Under USC 10th and AWWA M14 no psid value is entered on the report form for RP check #2 (M14 Table B-5 lists it as “tight, no psid determined”). Do not borrow the DC checks’ 1.0 psid floor for this step; exam language says tight against backpressure for a reason.

Where the “1.0 psid” myth comes from: a different ASSE-recognized procedure, NEWWA, adds an extra step that reconnects high to TC3 and low to TC4 and records a differential across check #2 with a 1 psid minimum. That step is real — but it belongs to NEWWA, not to USC 10th. On a USC 10th report form there is no psid blank for check #2. Know which procedure your school and your AHJ adopted, and answer written items in that frame; when a stem says “USC 10th,” the answer is tight or leaked.

Test 3 — Check #1 static differential

Goal: Measure the static differential across check #1 (inlet vs zone) under the approved static setup.

Meaning of the reading: After flow stops and conditions stabilize, check #1 should hold zone pressure below inlet pressure by a solid margin. That margin is what keeps the relief closed during normal service.

Pass idea (both parts required):

1. Check #1 differential ≥ 5.0 psid, and
2. Check #1 differential greater than the measured relief opening point from Test 1.

Example: relief opens at 2.3 psid; check #1 reads 5.1 psid → passes both floors. Relief opens at 2.3 psid; check #1 reads 4.8 psid → fails the 5.0 floor even though it is above relief. Relief opens at 2.8 psid; check #1 reads 5.2 psid → fails the “above relief” requirement even though 5.2 ≥ 5.0. Train yourself to check both inequalities every time.

Restore shutoffs and remove the kit safely

When readings are complete and documented:

1. Return the assembly to the in-service valve positions required by the owner (typically both shutoffs open unless a failed assembly must remain isolated per purveyor rules).
2. Close test cocks, remove hoses, and install test-cock plugs/caps.
3. Open shutoffs slowly to avoid water hammer; check for leaks at test cocks, shutoff packing, and relief.
4. Confirm the relief is not dumping continuously after restoration (if it is, the assembly may have been failing in service—document, do not “fix” by ignoring).
5. Leave the site with a clear pass/fail status for each component per your report form.

Field vs practical-exam mindset

On the job you still owe accurate numbers and ethical reporting. On the practical, you also owe clean sequence, no notes, and recovery from a staged fail mode. Practice the entire restore sequence under time pressure so you never leave shutoff #2 closed by accident after a “perfect” set of readings.

Master the USC 10th story of Test 1 → Test 2 → Test 3, lock the numeric criteria, and overlay your school’s exact valve steps until they are automatic.