Plumbing Pressure Tests: Water, Drains & Gas Are Different

01First separate operating pressure from test pressure

Operating pressure is what a system experiences in normal use. A test is a controlled check carried out under a specified procedure. A pipe's printed maximum rating is neither a recommended service setting nor permission to test the assembled system at that pressure.

A valid test record identifies the system, pipe and fitting products, test medium, pressure or water head, duration, temperature conditions, gauge or measuring method, isolated equipment and outcome. 'It held pressure' leaves out most of the information an inspector needs.

02Water supply: working pressure is not a universal test setting

EPA WaterSense recommends 45–60 psi service pressure for efficiency and describes the common requirement for regulation above 80 psi. These are normal-service references. They do not mean every new water line should be tested at 60, 80 or 100 psi.

The actual supply test depends on the adopted code, material, manufacturer's procedure and weakest connected component. Some PEX products require conditioning or stabilization, so the installer must use that exact system's instructions. Existing fixtures or appliances may need isolation; the test must not exceed their allowed exposure.

03Drain-waste-vent: feet of water head are not psi

Charlotte Pipe describes a 10-foot hydrostatic-head test, approximately 4.3 psi at a point 10 vertical feet below the water surface. That is a manufacturer example, not 10 psi and not 10 feet of horizontal pipe. Pressure changes with vertical depth, which matters for tall systems and sectioned testing.

The local authority must confirm the required water head, duration and acceptable procedure for the permit. This guide does not prescribe one hold time for every drainage system. Water-tightness also does not prove correct grade, venting, fitting selection or fixture-unit sizing.

Never use compressed air or gas to test PVC, CPVC or ABS. Charlotte Pipe warns of explosive failure, flying fragments and plug ejection. Older generic inspection handouts that mention air tests are not permission to disregard the material manufacturer's prohibition.

04Gas: a professional inspection test, not appliance pressure

As a named jurisdiction example, Roseville's 2025 gas-piping handout specifies at least 10 psi for at least 15 minutes with no perceptible pressure drop. This is not a claim that Santa Ana, Irvine or every project uses that exact procedure. The local inspector, gas supplier, system design and listed products control the actual requirements.

A test pressure must never be confused with an appliance's normal inlet pressure, which may be expressed in inches of water column. The qualified installer determines the approved nonfuel test medium, isolation, gauge selection and safe test procedure. Passing the inspection test does not by itself complete purging, reconnection, utility authorization or appliance commissioning.

05What to ask for at inspection

Before concealment, request the written test criteria and inspection stage from the contractor. If a city handout and a product manual appear to conflict, stop and resolve the discrepancy with the authority and manufacturer before testing—not by choosing the higher pressure.

Save the recorded results, visible-piping photos, equipment details and permit signoff. A photo of a gauge without a timestamped test record cannot establish how long the test held or which components were connected.

• System and material clearly identified
• Correct medium, pressure/head and hold time confirmed
• Sensitive components protected under the approved procedure
• Inspection acceptance and commissioning recorded separately