BackflowProof Field Guide
ASSE 5110 Backflow Test Report Form & Differential Pressure Math
How certified backflow testers evaluate 4-valve differential pressure readings, verify ASSE thresholds, and record pass/fail compliance in the field.
Understanding the ASSE 5110 Standard
The American Society of Sanitary Engineering (ASSE) Series 5000 / Standard 5110 establishes rigorous field evaluation procedures for backflow prevention assembly testers (BPATs).
Whether testing drinking water mains, commercial fire sprinkler systems, or landscape irrigation meters, every test requires measuring differential pressure across internal check valves and relief ports using a certified 3-valve or 5-valve differential pressure gauge.
Pass/Fail Thresholds by Valve Assembly Type
1. Reduced Pressure Zone (RPZ / ASSE 1013)
Installed on high-hazard cross connections (chemical plants, car washes, commercial boilers, hospitals).
- Check Valve #1: Must hold at least 5.0 psid (differential pressure).
- Check Valve #2: Must hold at least 1.0 psid against backpressure.
- Differential Relief Valve: Must open before differential drops below 2.0 psid.
- Shutoff Valve #2: Must hold drop-tight without leakage into the test chamber.
2. Double Check Valve Assembly (DCVA / ASSE 1015)
Installed on low-hazard or non-health hazard systems (fire sprinkler lines without chemical additives, commercial domestic bypasses).
- Check Valve #1: Must hold at least 1.0 psid.
- Check Valve #2: Must hold at least 1.0 psid.
- Shutoff Valve #2: Must hold drop-tight under backpressure.
3. Pressure Vacuum Breaker (PVB / ASSE 1020)
Installed on continuous pressure irrigation or industrial supply with no possible backpressure.
- Check Valve: Must hold at least 1.0 psid.
- Air Inlet Valve: Must open at least 1.0 psid above atmospheric pressure.
The Calibration Guard: Why Water Purveyors Reject Forms
One of the most frequent causes of rejected backflow compliance filings is an expired differential pressure gauge calibration.
Water purveyors and state EPAs mandate that field gauges (such as Mid-West 845 or Watts TK-9A) be calibrated annually (within 365 days) by an accredited laboratory. BackflowProof tracks tester calibration dates in real time and refuses to sign compliance reports if the gauge certification has lapsed.
Generate Clean Compliance Reports with BackflowProof
Instead of paper forms and evening math calculations, BackflowProof evaluates readings as you enter them in the vault.
You get instant pass/fail validation, automatic repair tracking if rubber discs were replaced, and a formal compliance narrative formatted for municipal inspectors.
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