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Quick answer: Charlotte Pipe recommends a water test for plastic drain, waste and vent (DWV) piping: plug the openings, fill from the highest point to 10 feet of head (4.3 psi), bleed out the air, then look at every joint. A leaking joint gets cut out and replaced. Never test ABS, CPVC or PVC with compressed air or gas.
- Vacuum test: Charlotte accepts testing ABS and PVC DWV to 8.75 inches of mercury, but says it is complex, needs dedicated equipment, and makes leaks hard to find.
- Smoke test: only from smoke-producing machines, never chemical smoke mixtures; hold 1 inch of water for 15 minutes or longer.
- Peppermint test: PVC DWV only. Charlotte says peppermint oil is not chemically compatible with ABS.
Steps come from Charlotte Pipe’s Plastics Technical and Installation Manual (pages 73–74), read October 9, 2026 from the rendered pages. Your local code and inspector set the required test; Charlotte says installers should always consider local conditions, codes and regulations. This page has no buy buttons.
Before you test
- Test after rough-in, before anything is covered. Charlotte says concealed work should stay uncovered until the required test is made and approved, and the water test should come before closing in the piping or backfilling underground pipe.
- Restrain the system at all bends, changes of direction and ends of runs.
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The water test, step by step
- Isolate the section. Insert test plugs through the test tees in the stack to isolate each floor or section. Plug or cap every other opening with test plugs or test caps.
- Foam core pipe: Charlotte says always use external caps, so water can’t leak through the foam core layer.
- Fill from the highest point, slowly. Filling slowly lets air escape as the water rises in the vertical pipe. Charlotte says all trapped air should be out before the test starts, or the results may be wrong.
- Bring it to 10 feet of head. Charlotte recommends testing at 10 feet of hydrostatic pressure, which is 4.3 psi.
- Inspect every joint by eye. If a joint leaks, Charlotte says cut it out and install a new section. For a square cut, see our pipe cutter guide.
- Drain and move on. Once a section passes, drain it and set up the next one.
Other test methods Charlotte covers
Vacuum test
Charlotte recognizes vacuum testing of ABS and PVC DWV to 8.75 inches of mercury as a safe practice. It also notes the method needs dedicated equipment, leak sites can be hard to find, and the industry has no efficient field method for it yet.
Smoke test (when an engineer, architect or code calls for it)
- Permanently connect all fixtures and fill all traps with water.
- Be ready to test the whole drainage and vent system, and close all windows until the test is done.
- Fill the system with thick smoke from one or more smoke-producing machines. Charlotte warns never to use chemical mixtures to make smoke.
- When smoke shows at the roof stack opening, close it.
- Keep adding smoke until pressure equals 1 inch of water, and hold it 15 minutes or longer.
- Check every point, connection and fixture: no smoke should be visible anywhere.
Peppermint test (PVC DWV only)
- Connect all fixtures, fill all traps, close all windows.
- Mix two ounces of peppermint oil with one gallon of hot water and pour it into the roof opening; close the opening tightly.
- Have someone other than the person who poured it check for peppermint odor. There should be none anywhere in the building.
Charlotte says this test is mostly used on older installations and must not be used on ABS DWV.
Testing water supply lines is different
For pressure (supply) systems, Charlotte says to test with water, anchor the piping with thrust blocking at changes of direction, size changes and dead ends, and fill slowly to avoid surges and trapped air.
FAQ
How many feet of head for a DWV water test?
Charlotte Pipe recommends testing at 10 feet of hydrostatic pressure, which is 4.3 psi. Your local code may set its own requirement.
Can I air test PVC drain pipe?
Charlotte says never test ABS, CPVC or PVC pipe or fittings with compressed air or gas, or with air-over-water boosters. Use a water test.
Can I do a peppermint test on ABS?
No. Charlotte says peppermint oil is not chemically compatible with ABS; use the peppermint test only on PVC DWV.
How long do you hold a smoke test?
Charlotte says build smoke pressure equal to one inch of water and maintain it for fifteen minutes or longer.
Related guides
Sources
- TM-PL (PDF) (charlottepipe.com), read 2026-10-09