Pressure Testing New/Repaired Piping: Maintenance Guide
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Pressure testing is a mandatory quality assurance procedure in which newly installed or repaired piping is filled with air or water and pressurized to a level above normal operating pressure for a specified duration to verify that all joints, connections, and pipe sections are leak-free before the system is concealed behind walls, under slabs, or placed into service. Pressure testing is required by the applicable state building codes and must pass inspection before the plumbing can be covered.
Hold-Pressure Principle, Water Supply & DWV Test Protocols
The fundamental principle of pressure testing is straightforward: if the system holds pressure without dropping over the test period, no leaks exist. A pressure drop indicates that air or water is escaping through a failed joint, cracked fitting, or defective pipe section that must be identified and repaired before retesting.
For water supply piping, the standard test protocol involves capping all open fixture connections, filling the system with water to purge air, and then pressurizing the system to the test pressure using a hand pump or compressor. The test pressure for potable water piping under the applicable state building codes is 1.5 times the working pressure or 150 PSI, whichever is greater, held for a minimum of 15 minutes with no visible leaks and no pressure drop.
For drain, waste, and vent (DWV) piping, the test method differs. DWV systems are tested with either water or air. The water test fills the system to the highest vent opening and observes for level drop over 15 minutes. The air test pressurizes the DWV system to 5 PSI and holds for 15 minutes. DWV air tests use lower pressure because drain piping is not designed for sustained internal pressure.
Gas piping pressure tests use higher test pressures held for longer durations. The National Fuel Gas Code requires a minimum 3 PSI test for 10 minutes on residential gas piping systems.
Hydrostatic, Pneumatic, Vacuum & Isolation Testing Methods
Hydrostatic testing fills the system with water and pressurizes it. This is the most common method for water supply piping because water is incompressible — a leak causes an immediate, measurable pressure drop. It is also safer than air testing because water releases very little stored energy if a fitting fails.
Pneumatic (air) testing pressurizes the system with compressed air. Air testing is used for DWV systems and for supply piping in freezing conditions where water would damage the system. Air is compressible, so it stores significant energy under pressure, making pneumatic tests at high pressures potentially hazardous.
Vacuum testing applies negative pressure to detect leaks in sealed systems, most commonly used for medical gas piping and specialty laboratory plumbing.
Isolation testing pressurizes individual sections or zones of a larger system to narrow down the location of a suspected leak. This method is used when a whole-system test fails and the plumber needs to identify which zone contains the failure.
Permit Inspection, Defect Repair & Iterative Testing Services
Pressure testing is a required step in every new installation and repair project. Bonded Plumbworks’ technicians perform pressure tests on all repiping projects, new construction rough-ins, water heater replacements, and gas line installations. The test results are documented and presented to the local building inspector as part of the permit inspection process.
When a pressure test reveals a failed joint, Bonded Plumbworks identifies and repairs the defect, then retests the entire section. This iterative process continues until the system achieves a clean pass, ensuring that no concealed leaks will cause water damage, mold growth, or gas hazards after the walls are closed.
State Plumbing Code, NFPA 54, ASTM F2164 & IPC Section 312
The applicable state building codes — Plumbing edition requires hydrostatic testing of potable water systems at 1.5 times working pressure for 15 minutes. The National Fuel Gas Code (NFPA 54) requires gas pipe testing at 3 PSI for 10 minutes. ASTM F2164 covers field leak testing of polyethylene piping. The International Plumbing Code (IPC) Section 312 specifies DWV testing methods and acceptance criteria.
Reed, Wheeler-Rex & RIDGID Hydrostatic Test Pump Equipment
Reed Manufacturing produces the DrillPress hand test pump for hydrostatic testing. Wheeler-Rex manufactures the 29200 electric hydrostatic test pump rated to 300 PSI. Yellow Jacket (Ritchie Engineering) offers digital manifold gauges for precision pressure monitoring. RIDGID produces the 1460 pressure test pump for residential and light commercial applications.