System Testing, Inspection, and Troubleshooting
System Testing, Inspection, and Troubleshooting asks you to prove the work and then diagnose failures from the symptom.
Tests you must know
- DWV water test: fill to 10 ft of head above the highest point, hold 15 minutes, no drop. Plug or cap all openings and restrain the plugs.
- DWV air test where permitted: typically about 5 psi with a gauge on the system for 15 minutes. It is dangerous on plastic if the cement is not fully cured, so never over-pressurize.
- Water supply: hydrostatic test at 100 psi, or working pressure plus a margin, for 60 minutes; read the gauge, not the joint.
- Gas piping: a separate test at the pressure the code sets for the system size, with the gauge isolated from the source.
- Smoke or peppermint for vents; dye and camera for drain leaks.
Inspection flow
- Rough-in before concealment: verify slope, strap spacing, cleanouts, vent height, firestopping at penetrations, and access to valves.
- Final: run water at the farthest fixture, check flow and temperature, verify fixture security and trap seals, and look for leaks at the meter.
Troubleshooting by symptom
- Gurgling and slow drains at many fixtures: main line or building vent blockage, not a fixture trap.
- Sewer odor in one bathroom: a dry trap or a wet vent that has lost its seal.
- Banging on shutoff: water hammer from missing arrestors or a failed PRV.
- T&P discharge with no overheating: closed system without an expansion tank.
Worked example
Top-floor fixtures drain slowly while lower-floor fixtures are fine. The suspect is the stack vent or a blockage in the stack above the highest lower-floor connection: lower fixtures still drain by gravity into an unobstructed lower stack, while the top floor pulls air through the restriction.
Traps
Air-testing plastic DWV at high pressure, testing before solvent cement cures, accepting a pressure drop without checking gauge temperature effects, and covering a joint that failed.