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BLD-PLUM06-08 · Lesson 12 · 8 clock hours · practice

ASSE Backflow Tester Examination Readiness and Mock Test

Objective. The learner completes a timed 50-question mock examination covering hydraulic principles, assembly selection, field test procedures, and repair, scoring at least 75%, and performs one complete RPZ field test from memory within the time limit.

Why This Lesson Matters

You are one lesson away from sitting the ASSE Backflow Tester examination. This session pulls every major content area together so you can demonstrate—under timed, closed-book conditions—that you are ready to protect public health in the field. The ASSE credential is portable and recognized by water purveyors, municipalities, and employers nationwide, but it carries a real responsibility: an incorrect test result or a missed repair leaves a cross-connection open to contamination. Accuracy matters more here than in almost any other plumbing task.

What the ASSE Backflow Tester Exam Tests

The examination covers four interlocking content domains. You must be competent in all four.

Hydraulic principles. You must understand the difference between backpressure and backsiphonage, how pressure differentials drive flow reversal, and why degree of hazard determines which assembly is required. Know that high-hazard connections (toxic or health-threatening substances) demand a higher level of protection than low-hazard connections.

Assembly identification and selection. Each backflow prevention assembly has a specific application envelope. The reduced-pressure zone (RPZ) assembly is required for high-hazard applications and provides protection against both backpressure and backsiphonage. The double-check valve assembly (DCVA) is used for low-to-moderate hazard applications. Pressure vacuum breakers (PVBs) and atmospheric vacuum breakers (AVBs) protect only against backsiphonage and must be installed above the highest downstream outlet. You must be able to select the correct assembly for a described scenario.

Field test procedures. ASSE 5013 defines the standard test procedures for field-testing backflow prevention assemblies. You must know the correct sequence of steps, what each differential pressure reading means, and how to interpret results to determine pass or fail. You cannot use notes during the exam or during a witnessed field test.

Repair and maintenance. If an assembly fails its field test, you must know which components are suspect, how to disassemble and inspect check valves and relief valves, and when an assembly must be replaced rather than repaired. Only parts approved for the specific assembly model may be used.

The RPZ Field Test: Sequence From Memory

The RPZ assembly contains two spring-loaded check valves and a differential pressure relief valve (DPRV). The standard field test verifies that both checks hold and that the relief valve opens at the correct differential. Work through this sequence until it is automatic.

1. Site inspection. Confirm the assembly is the correct type and size for the application, check for physical damage, and verify the shutoff valves are operable.

2. Attach the test kit. Connect the differential pressure gauge hoses to the test cocks in the correct order per ASSE 5013; bleed air from the hoses before recording any reading.

3. Test check valve No. 2 (downstream check). Perform the procedure specified in ASSE 5013; note the differential pressure and compare to the pass/fail threshold.

4. Test check valve No. 1 (upstream check). Perform the procedure; note the differential pressure.

5. Test the differential pressure relief valve (DPRV). Determine whether the relief valve opens at or above the required differential.

6. Restore the assembly. Remove the test kit, close test cocks, confirm the assembly is back in full service.

7. Complete the field test report form. Record all readings, pass/fail determinations, and sign the form. An incomplete or unsigned form is unacceptable.

If any reading falls outside the acceptable range, the assembly fails that test. Document the failure, notify the water purveyor or owner as required, and follow your jurisdiction's procedure for tagging or removing a failed assembly from service.

Safety During Field Testing

Personal protective equipment. Wear safety glasses whenever you open test cocks—pressurized water can spray unexpectedly. Gloves protect against hot or cold water burns.

Lockout/tagout (LOTO). If you must disassemble any assembly for repair, isolate the water supply and follow your facility's energy control program before opening any union or removing any component. Never assume pressure has been relieved; verify with a gauge.

Calibrated equipment. A test kit that is out of calibration produces unreliable readings. Check your kit's calibration date before every testing session. An incorrect reading can result in a contaminated cross-connection remaining in service—a direct public-health hazard.

Test cock safety. Always open test cocks slowly and direct discharge away from electrical panels and slip hazards.

Examination Day Strategy

Read every question completely before selecting an answer. Hydraulic calculation questions—such as those asking you to compare pressures at two points—reward careful unit tracking. Eliminate obviously wrong distractors first. If you are unsure, mark the question and return to it; do not leave any answer blank.

For the practical component, talk through each step quietly if your nerves interfere with recall. Instructors are scoring your sequence and your final determination—they are not there to trick you. A confident, methodical approach earns full marks even if you work at a measured pace.

Clearing the Course

Both components must meet the standard: 37 of 50 questions correct (75%) on the mock examination, and all critical steps completed in correct sequence with a correctly determined pass/fail result on the timed RPZ field test. A strong score on one component does not compensate for failure on the other. This mirrors the real ASSE examination structure, where written and practical competence are both required.

Key terms10

Reduced-Pressure Zone (RPZ) AssemblyA backflow prevention assembly containing two independently operating spring-loaded check valves and a differential pressure relief valve; required for high-hazard cross-connections and protects against both backpressure and backsiphonage.
Differential Pressure Relief Valve (DPRV)The relief valve within an RPZ assembly that opens to atmosphere when the pressure in the zone between the two checks drops to or below the upstream supply pressure, ensuring the zone never pressurizes to a level that could force contaminated water back upstream.
BacksiphonageA form of backflow caused by negative pressure (partial vacuum) in the supply piping, which draws downstream water or contaminants back into the potable supply.
BackpressureA form of backflow in which downstream pressure exceeds supply pressure, forcing non-potable water or substances back into the potable system.
ASSE 5013The ASSE International standard that defines field test procedures for backflow prevention assemblies; the authoritative procedural reference for certified backflow tester examinations and field work.
Double-Check Valve Assembly (DCVA)A backflow preventer containing two independently operating spring-loaded check valves; approved for low-to-moderate hazard applications and protects against both backpressure and backsiphonage, but not approved for high-hazard connections.
Degree of HazardA classification of the potential health risk posed by a cross-connection; high-hazard connections involve toxic or health-threatening substances and require a higher level of backflow protection than low-hazard connections.
Test CockA small shutoff valve built into a backflow prevention assembly specifically to allow attachment of field-test equipment without removing the assembly from service.
Field Test Report FormThe official document required by ASSE and most water purveyors on which the tester records all differential pressure readings, pass/fail results, the assembly's identification data, and the tester's signature; an unsigned or incomplete form is not acceptable.
CalibrationThe process of verifying and adjusting a test kit's differential pressure gauge against a known standard so that field readings are accurate; a test kit that is out of calibration must not be used for official field testing.

Worked examples4

1. An RPZ assembly is being field-tested. The supply pressure at test cock No. 1 reads 85 psi. After performing the check valve No. 1 test procedure, the gauge reads a differential of 7.0 psi across check No. 1. The minimum acceptable differential for check No. 1 is 5.0 psi. Does check No. 1 pass or fail?
  1. Step 1: Identify the pass/fail threshold for check No. 1. The minimum differential pressure that check No. 1 must hold is 5.0 psi.
  2. Step 2: Compare the measured differential to the threshold. Measured differential = 7.0 psi; threshold = 5.0 psi.
  3. Step 3: Since 7.0 psi ≥ 5.0 psi, the check valve is holding more than the minimum required differential.
Answer: Check No. 1 passes. The measured differential of 7.0 psi exceeds the 5.0 psi minimum, meaning the check valve is seating properly and resisting backflow.
2. During the same test, check valve No. 2 is tested and the measured differential is 2.8 psi. The minimum acceptable differential for check No. 2 is 1.0 psi. The differential pressure relief valve (DPRV) is then tested; it opens at a differential of 3.5 psi measured from supply to the zone. The minimum required opening differential for the DPRV is 2.0 psi. Record the overall test result.
  1. Step 1: Evaluate check No. 2. Measured = 2.8 psi; minimum = 1.0 psi. 2.8 ≥ 1.0, so check No. 2 passes.
  2. Step 2: Evaluate the DPRV. The DPRV must open at or above the minimum differential of 2.0 psi. Measured opening differential = 3.5 psi. 3.5 ≥ 2.0, so the DPRV passes.
  3. Step 3: Review all three components. Check No. 1: pass (from previous example). Check No. 2: pass. DPRV: pass.
  4. Step 4: All three components passed their respective tests, so the assembly as a whole passes.
Answer: The RPZ assembly passes the complete field test. All three components—check No. 1, check No. 2, and the DPRV—met or exceeded their minimum differential pressure requirements. Record all readings and the overall PASS determination on the field test report form and sign it.
3. A tester re-tests the same RPZ the following year. This time check No. 2 reads only 0.6 psi differential (minimum is 1.0 psi), and the DPRV does not open during the test procedure. What is the result and what must the tester do?
  1. Step 1: Evaluate check No. 2. Measured = 0.6 psi; minimum = 1.0 psi. 0.6 < 1.0, so check No. 2 fails.
  2. Step 2: Evaluate the DPRV. If the DPRV does not open when it should, it has failed to perform its protective function—the assembly fails this component.
  3. Step 3: Because at least one component has failed, the entire assembly fails the field test regardless of any passing components.
  4. Step 4: Document all readings and mark the overall result as FAIL on the field test report form. Notify the owner and the water purveyor per local requirements, and follow jurisdiction procedures for tagging or taking the assembly out of service until it is repaired or replaced and retested.
Answer: The assembly fails. Check No. 2 (0.6 psi < 1.0 psi minimum) and the DPRV both failed. The tester must complete and sign the field test report form recording all readings and the FAIL determination, notify the responsible parties, and ensure the cross-connection is managed per local requirements until a passing retest is achieved.
4. A pressure vacuum breaker (PVB) is installed on an irrigation system. The outlet of the last irrigation head is at an elevation of 24 inches above grade. The PVB body is installed at 18 inches above grade. Is this installation compliant with the basic installation requirement for a PVB?
  1. Step 1: Recall the PVB installation rule. A PVB must be installed so that the critical level of the assembly is above the highest downstream outlet or use point.
  2. Step 2: Identify the relevant elevations. PVB critical level = 18 inches above grade. Highest downstream outlet = 24 inches above grade.
  3. Step 3: Compare. 18 inches is less than 24 inches, meaning the PVB body is below the highest outlet.
Answer: No, the installation is not compliant. The PVB is 6 inches lower than the highest downstream outlet (18 in vs. 24 in). Under backsiphonage conditions, contaminated water from the irrigation head could siphon back through the PVB. The assembly must be relocated so its critical level is above 24 inches.
In class: Instructor-facilitated review session: learners identify their weakest areas from prior lesson assessments; instructor provides targeted review using flashcards and whiteboard problem-solving for those topics · Timed mock examination: learners complete 50 multiple-choice questions mirroring ASSE Backflow tester exam content areas (no notes); papers scored immediately with class debrief on missed items · Timed field test performance: each learner independently performs one complete RPZ field test from initial inspection through final form sign-off within a set time limit; instructor observes and scores on a procedural checklist
Materials: Printed 50-question mock exam (instructor-developed from ASSE content domains); answer key; calibrated test kits; RPZ assemblies on training rigs; ASSE standard field test report forms; timer; NCCER Plumbing Level 3–4 textbook; ASSE 5013
Check: Mock exam: minimum score of 75% (37 of 50 correct); timed RPZ field test: all critical steps completed in correct sequence with no safety or procedural omissions and a correctly determined pass/fail—both components must meet standard to clear the course

Practice check8

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

Assembly identification and selection
1. Which backflow prevention assembly is required when a cross-connection involves a high-hazard substance and must protect against both backpressure and backsiphonage?
Field test procedures
2. During an RPZ field test, check valve No. 1 holds a differential of 4.2 psi and the minimum acceptable differential is 5.0 psi. What is the correct determination?
Hydraulic principles
3. What is the primary function of the differential pressure relief valve (DPRV) in an RPZ assembly?
Field test procedures
4. A field tester opens a test cock and does not bleed air from the hose before recording a differential pressure reading. What is the most likely consequence?
Repair and maintenance
5. A plumber is about to disassemble an RPZ assembly for repair. Before removing any union, which safety procedure must be followed?
Assembly identification and selection
6. A pressure vacuum breaker (PVB) is installed at 30 inches above grade. A hose bib downstream is at the same elevation. An irrigation head downstream reaches a maximum height of 36 inches during operation. Which statement correctly evaluates this installation?
Field test procedures
7. After completing an RPZ field test in which the assembly fails, what must the tester do with the field test report form?
Hydraulic principles
8. Backsiphonage differs from backpressure in that backsiphonage is caused by:
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