How to Test a Backflow Preventer

Why this matters

Backflow prevention devices (RPZ, DCVA, PVB) protect potable water from contamination by isolating the home water supply from irrigation, fire sprinkler systems, boilers, + commercial water connections. Municipal water authorities require annual testing for many installations. Each test runs a modest fee for 30-45 min on-site work. Plumbers with certification often handle 100-300 tests per year, adding up to meaningful recurring revenue from minimal travel. This is the working procedure.

Why backflow happens

Two scenarios pull contaminated water back into the supply:

Back-siphonage: a drop in supply pressure (water main break, large fire-pump draw, repair work) creates negative pressure. Water in connected fixtures siphons backward.

Back-pressure: a pump, boiler, or pressurized tank creates higher pressure than supply, forcing water back.

Without backflow prevention: irrigation water with fertilizer, boiler glycol, septic-tank effluent could enter potable supply. Real-world incidents have caused illness + death.

Common backflow devices

RPZ (Reduced Pressure Zone) assembly:

• 2 spring-loaded check valves + 1 relief valve
• Protection: high hazard (Class 5 - septic, fertilizer, boilers with glycol)
• Must be installed above grade
• Annual test required
• The most expensive device of the four

DCVA (Double Check Valve Assembly):

• 2 spring-loaded check valves in series
• Protection: low-medium hazard (Class 1-4 - irrigation without injection, fire sprinkler without antifreeze)
• Can be in vault or above grade
• Annual test required
• Mid-priced device, well below an RPZ

PVB (Pressure Vacuum Breaker):

• Single check + air-inlet valve at outlet
• Protection: back-siphonage only (NOT back-pressure)
• Installed 12" above highest downstream outlet
• Common on residential irrigation
• Priced below a DCVA

AVB (Atmospheric Vacuum Breaker):

• Simplest, no moving parts, single shutoff vent-to-atmosphere
• Hose-bib backflow preventer common type
• The cheapest device of the four
• Generally not testable; replace if damaged

Tools

• Test gauge kit (Watts TK99, Conbraco 4-valve, etc.) - the primary equipment investment
• Calibration certificate (annually required)
• Phillips + flathead drivers
• Pipe wrench
• Test reports (paper or digital)
• Soap solution (leak verification)
• Backflow tester certification (required in most jurisdictions)

Certifications

Most jurisdictions require backflow testers to be certified:

• ABPA (American Backflow Prevention Association): national
• ASSE 5000 series + 6000 series
• State + local programs (Texas requires TCEQ certification; California has individual local programs; etc.)

Certification cost: a few hundred dollars plus 24-40 hours of training. Test fees run a modest amount per device. Pays back in 4-8 jobs.

Renewal annually or biennially per jurisdiction.

Procedure - RPZ test

Step 1: Identify device

1. Brand + model + size
2. Serial number for records
3. Photo of installation
4. Inlet vs outlet identification

Step 2: Connect gauge

RPZ test ports: typically 4 small valves on side (test cocks):

• Test cock #1: upstream of first check
• Test cock #2: between checks
• Test cock #3: after second check
• Test cock #4: relief valve port

Connect gauge to test cocks per gauge kit manual.

Step 3: Test sequence

Per ASSE 5013 procedure:

1. Bleed gauge
2. Open shutoff valve #2 (closes #1)
3. Test relief valve: should open at specified delta-P
4. Test first check: should hold pressure differential
5. Test second check: should hold pressure differential
6. Document each reading

Step 4: Document

• Pass / fail per criteria
• Each reading recorded
• Signed by tester
• Submitted to water authority

If fail: identify which component (first check, second check, relief valve). Repair or replace. Re-test.

Procedure - DCVA test

Step 1: Connect

DCVA test ports: 4 test cocks similar to RPZ.

Step 2: Test

Per procedure:

1. Bleed gauge
2. Test first check: should hold differential pressure
3. Test second check: should hold differential pressure
4. Record both

Step 3: Document

Pass/fail + readings.

Procedure - PVB test

Step 1: Connect

PVB has 2 test cocks + a shutoff valve.

Step 2: Test

Per procedure:

1. Close shutoff valve
2. Test cock #1: should hold pressure
3. Open shutoff valve
4. Air-inlet should close at specified pressure threshold

Step 3: Document

Pass/fail.

Reporting

Most water authorities require:

• Test results submitted within 5-10 days of test
• Online portal OR paper form
• Tester certification number on report
• Customer copy

Failure to submit report: customer water service can be shut off until compliance.

Some authorities work directly with backflow companies via API or portal. Set up customer accounts.

Common service issues

Relief valve dripping (RPZ):

• First check failing OR debris in check
• A low-cost repair kit OR new check valve
• Test re-passes after repair

Pressure drop through device:

• Restricted flow downstream
• Spring degradation
• Device replacement OR rebuild

Vacuum breaker stuck open:

• Debris in valve
• Replace seal or device

Device installed wrong direction:

• Common on customer-installed irrigation backflow
• Re-pipe correctly

Repair vs replace

Rebuild kits are typically faster than replacement for serviceable RPZ + DCVA. PVBs often replace entire device.

Common pitfalls

• Wrong gauge calibration: invalidates tests + can lose certification
• Forgotten test submission: customer water service shut off; angry call
• Skipping seasonal isolation valve verification: blamed for "leaking shutoff" you didn't service
• No customer signature: dispute risk
• Test in winter on outdoor device: device frozen + cracked
• No PPE for chemical-contaminated water: don't service without protection

Customer talking points

For required annual test:

1. "City requires annual test; we handle the certification + submission."
2. "Test takes 30-45 minutes; you stay in business during testing."
3. "If passes: report submitted, you're compliant for the year."
4. "If fails: I can repair on the spot or schedule return - typically a modest amount additional."

For property managers with many properties:

1. "We track all backflow devices in your portfolio + handle annual scheduling."
2. "Bulk pricing: $X per device across your buildings."
3. "Includes failure repair + retest at preferential rates."

Recurring revenue + minimal travel between sites makes this a tier-1 plumbing business.

Seasonal considerations

Backflow devices freeze in cold climates:

• Outdoor PVBs + DCVAs especially vulnerable
• Insulated covers or seasonal removal recommended
• Bonded boxes (water-shedding cover) prevent freeze damage
• Schedule fall winterization + spring activation as separate service

References

• ASSE 5013 (RPZ test procedure)
• ASSE 5012 (DCVA test procedure)
• ASSE 5011 (PVB test procedure)
• AWWA C512 (devices + standards)
• State + local water authority requirements
• Backflow tester certification programs (ABPA, state-specific)
• Manuall internal: Backflow Preventer Reference, Annual Whole-Home Plumbing Inspection