7.3 Inspections and Tests: DWV, Water, Sewers, Storm, Shower Pans & Backflow

Why this section matters

Testing questions fall under System Installation and General Knowledge. Almost every number lives in IPC 312, and 15 minutes is the hold time for every DWV, water, sewer and shower-pan test. The hard part is matching the right medium and pressure to each system, and remembering what the 2021 code no longer allows, such as air-testing plastic.

Inspection stages

The IPC's administrative chapter (Chapter 1, "Required Inspections and Testing"), as adopted by the local jurisdiction, calls for:

1. Underground inspection: after trenches are dug and bedded and piping is installed, before backfill.
2. Rough-in inspection: after the roof, framing, fireblocking, firestopping, draftstopping and bracing are in place and all sanitary, storm and water piping is roughed in, before wall or ceiling membranes go on.
3. Final inspection: after the building is complete, all fixtures are set and connected, and the structure is ready for occupancy.

The permit holder must request inspections and keep the work visible and accessible until it is approved. Work may not proceed past an inspection point without approval. In Alabama, local building departments issue permits and inspect, while the Board licenses the workers. Under rule 720-X-11-.01, a registered apprentice works under the direct supervision of a journeyman or master who stays on the job site. One supervisor may oversee up to 5 apprentices on a residential jobsite and up to 3 on other jobsites.

General test rules (312.1)

• The permit holder performs the tests, gives the code official reasonable notice, and furnishes the equipment, materials, power and labor.
• Piping is tested with water, or, for piping other than plastic, with air.
• After fixtures are set and traps filled, the whole drainage system gets its final test.
• The code official may require cleanouts to be removed to confirm that the pressure reached every part of the system.

Test gauges (312.1.1):

DWV tests (312.2–312.4)

Water test (312.2):

• Whole system: close every opening except the highest, and fill to the point of overflow.
• In sections: plug every opening except the highest in the section, and give each section at least a 10-foot head of water. When testing the next section up, retest at least the upper 10 feet of the section below. That way every joint except the top 10 feet of the system sees a 10-foot head.
• Hold for at least 15 minutes, with the system tight at all points.
• A 10-foot head is about 4.3 psi at the bottom of the section (10 × 0.433).

Air test (312.3):

• Plastic piping shall not be tested using air. If plastic fails under compressed air it can shatter, so plastic DWV is water-tested.
• Pump air to a uniform 5 psi, or enough to balance a 10-inch column of mercury, and hold for 15 minutes.
• Make any adjustments for temperature changes or gasket seating before the test period starts.

Final test (312.4):

• The final test of the completed drainage and vent system is visual, in enough detail to confirm code compliance.
• Where a smoke test is used:
  1. Fill all traps with water.
  2. Introduce pungent, thick smoke from one or more smoke machines.
  3. When smoke appears at the stack openings on the roof, close them.
  4. Hold 1 inch of water column for 15 minutes.

(Older codes also described a peppermint test. It is not in the 2021 IPC.)

Water supply test (312.5)

• Test a completed section or the whole system under a water pressure no less than the system's working pressure.
• Or, for piping other than plastic, use an air test of at least 50 psi.
• Hold for 15 minutes. Water for the test must come from a potable source.
• A 50 to 100 psi test needs a gauge in 1-psi increments.
• After testing, disinfect the system per 610.1 before it is used.

Sewer, storm, shower pan and backflow tests

Common failure points

• Water test leaks at unglued plastic joints, loose hubless couplings, cracked fittings and the test plugs themselves. Recheck the plugs first.
• A dropping air gauge on metal piping may be temperature change. That is why adjustments are made before the timed period starts.
• Shower pans leak where the liner was nailed below the threshold or the drain clamp ring was not tightened. Section 421.5.2 bans nails within 1 inch above the threshold.
• Never cover or conceal work that failed a test or has not been approved.

Exam traps

• No air test on plastic (312.3). Use the water test.
• DWV air test 5 psi; water supply air test 50 psi (and not on plastic).
• Water supply water test is at working pressure, not a fixed 50 psi.
• Gravity sewer: 10-foot head of water only. Forced sewer: 5 psi above the pump rating.