Test Equipment & Calibration
Differential pressure gauges, test kit components, calibration requirements, needle valves, and hose management.
- Identify the components of a standard backflow test kit
- Explain how a differential pressure gauge measures pressure differential
- State the calibration frequency and accuracy requirements for test gauges
- Describe proper hose flushing and air bleeding procedures
- Maintain and care for test equipment to ensure accurate readings
Lección 1
Test Kit Components & Differential Pressure Gauges
The Backflow Test Kit
Every ASSE 5110 tester uses a differential pressure test kit to perform field tests per ASSE/IAPMO/ANSI Series 5000-2022. The 2022 standard (7th edition field test procedures booklet) governs both 3-valve and 5-valve test kits. The test kit is the primary tool of the backflow tester and must be properly maintained and calibrated. A standard test kit includes:
- Differential pressure gauge - the core measurement instrument
- Three hoses - color-coded to connect to test cocks on the assembly
- Needle valves - precision flow control valves on the test kit manifold
- Bleed valves - to vent air from hoses and equalize pressure
- Fittings and adapters - to connect to various test cock sizes
How the Differential Pressure Gauge Works
The differential pressure gauge does not read absolute pressure. It measures the difference in pressure between two points. When connected across a check valve, it shows how much higher the upstream pressure is compared to the downstream pressure. This differential is what determines whether a check valve is holding.
For example, if the pressure upstream of Check #1 is 65 psi and the pressure downstream of Check #1 is 60 psi, the differential pressure gauge reads 5.0 psi - meaning the check valve is holding a 5.0 psi differential.
Gauge Reading Principle
The gauge reads the difference between high and low side. A reading of 0.0 psi means no difference - the check valve is not holding. A reading above the minimum threshold means the check valve is functioning. The needle valves on the test kit control which pressure points are connected to the gauge.
Needle Valves
The test kit's needle valves are precision valves that the tester opens and closes in specific sequences to route pressures to the gauge. Each test procedure requires opening and closing needle valves in a particular order. The needle valves are typically numbered and correspond to the test cocks on the assembly.
Proper needle valve operation is critical - opening the wrong valve at the wrong time can give a false reading or damage the gauge.
The differential pressure gauge measures the pressure difference between two points, not absolute pressure. The test kit uses needle valves to control which pressures are routed to the gauge. A higher differential reading means the check valve is holding stronger.