Duplex Slab Rough-In: Invalid Tests and Uninspected Underground
A contractor calls for a rough-plumbing inspection on a new duplex before the slab is poured. The underground DWV was installed two weeks earlier but was never inspected; the contractor says it “looked fine” and covered it with gravel. The above-floor DWV has been filled with water to 3 feet above the highest point and held for 10 minutes. The domestic water piping was tested at 60 psi for 30 minutes. The gas piping was tested at 10 psi for 15 minutes. The slab is scheduled for tomorrow, and the contractor wants a single approval so the concrete can proceed. The plans show a 2-inch vent through the roof and a 4-inch building drain.
1. Evaluate the DWV, water-supply, and gas tests against UPC-type requirements.
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The DWV water test is inadequate. The usual UPC water test requires the system to be filled to at least 10 feet above the highest point of the piping under test and held for at least 15 minutes. A 3-foot head held for 10 minutes does not meet that standard and would not reliably reveal leaks at the lower joints.
The water-supply test is also inadequate. The usual requirement is a hydrostatic test at not less than 100 psi for at least 1 hour, or an approved equivalent method. Testing at 60 psi for 30 minutes is below the standard and should not be accepted.
The gas test at 10 psi for 15 minutes is the one test that appears to meet the common UPC requirement, assuming the gauge held, the system was isolated, and all joints were exposed. The inspector should still verify the gauge and test setup. Even if the gas test is acceptable, it does not cure the invalid DWV and water tests.
2. What is the proper inspection sequence, given that the underground DWV was never inspected?
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The underground DWV must be inspected before it is covered. “It looked fine” is not an inspection. Because the piping is covered with gravel, the contractor should remove the gravel or provide access so the inspector can examine the pipe material, fittings, slope, bedding, joints, and connections to the building drain. If portions cannot be exposed, the inspector should not approve them based on the contractor’s assurance.
The sequence should be: inspect the underground DWV and any underground water or gas piping; correct deficiencies; test the DWV and water piping at the required pressure and duration; inspect the above-floor rough-in; verify venting and support; then approve the slab pour. The gas test can be reviewed separately, but it should not be used as a reason to skip the underground inspection.
A single approval for the entire slab is not appropriate while the underground work is uninspected and the DWV and water tests are invalid.
3. Can the inspector grant a single rough approval so the concrete can proceed? Explain how to document the decision.
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No. The inspector should not grant a single rough approval when required underground work is concealed and uninspected and when two required tests are below code. Granting approval would allow concrete to cover work that has not been verified.
The inspector should issue a written correction notice identifying the uninspected underground DWV, the inadequate DWV test, and the inadequate water-supply test. The notice should require exposure of the underground piping, a proper DWV test at the required head and duration, a proper water test at the required pressure and duration, and reinspection before the slab is poured. If the gas test is valid, it can be noted as accepted, but final approval should remain withheld until all items are corrected.
Documentation should include the inspection date, the contractor’s request for a single approval, the specific test pressures and durations observed, the fact that the underground was covered before inspection, and the reinspection requirements. The record should clearly state that concrete placement is not approved until the corrections are complete.