Lesson 14: Tests, Inspections, and Course Review

Reading

Thirteen lessons have taught how a commercial plumbing system is sized, vented, drained and supplied. Two parts of the 2021 IPC prove that the finished work matches the design. Section 312 says how each system is tested for leaks, and Section 108 says who inspects, at what point, and what must stay uncovered until they do. This last lesson teaches both, then reviews the whole course module by module. Texas cities choose their own plumbing code and Houston enforces the Uniform Plumbing Code (Lesson 1), so treat every number here as a 2021 IPC value and confirm the adopted code and any local test rules before you rely on one.

Who tests, and who watches

Section 312.1 puts the test on the permit holder. The holder gives the code official reasonable advance notice that the work is ready, furnishes the equipment, material, power and labor, and is responsible for knowing that the work will withstand the test pressure. Section 108.4 adds that the code official observes the test, and 108.4.2 repeats that the holder furnishes everything. Piping is tested with water or, for piping systems other than plastic, with air. After the fixtures are set and their traps are filled with water, the whole drainage system gets a final test. Where necessary, the code official requires cleanouts to be removed to show that the pressure reached every part of the system (312.1).

The drain and vent water test (312.2)

A water test can cover the whole system or one section at a time. To test the whole system, close every opening except the highest and fill the system to the point of overflow. To test in sections, plug every opening except the highest ones in the section under test and fill that section, but never with less than a 10-foot head of water. As the test moves up the building, the upper 10 feet of the section just tested is tested again with the next one, so that no joint or pipe, except the uppermost 10 feet of the system, sees less than a 10-foot head. The pressure is held not less than 15 minutes, and the system must then be tight at all points. A column of water 10 feet high is 4.33 psi (Lesson 7), so this is a gentle test, read by the water level and a dry joint and not by a gauge.

The air test and its limit (312.3)

Air is the alternative where a water test is not practical, but plastic piping is never tested with air. The test forces air into the system until there is a uniform gauge pressure of 5 psi, or enough to balance a 10-inch column of mercury, and holds it not less than 15 minutes. Any adjustment for a change in ambient temperature or for the seating of gaskets is made before the 15 minutes begin, so a cooling pipe does not cause a false failure. On a job with plastic drain and vent piping, the plastic rule leaves the water test as the only choice.

The final test and the smoke test (312.4)

The final test of the completed drainage and vent systems is visual and detailed enough to judge compliance with the code. If a smoke test is used, all traps are filled with water and a pungent, thick smoke from one or more smoke machines goes into the entire system. When smoke shows at the stack openings on the roof, those openings are closed and a pressure equal to a 1-inch water column is held for not less than 15 minutes. Because this test runs after the fixtures are set, it checks the finished system and not just the pipe in the wall.

The water supply test (312.5)

A completed section of the water supply system, or the whole system, is tested and proved tight under a water pressure not less than the working pressure of the system. For piping systems other than plastic, an air test of not less than 50 psi is the alternative. Either pressure is held not less than 15 minutes, and the test water must come from a potable source, because it wets pipe that will carry drinking water. For example, a system behind a pressure-reducing valve set at 65 psi has a working pressure of 65 psi (Lesson 6), so the test is not less than 65 psi. Ask the inspector how the local office reads working pressure before the day of the test.

Building sewers and storm drains (312.6 to 312.8)

Both building sewer tests plug the end of the sewer at the point where it meets the public sewer. A gravity sewer is filled with water to a head of not less than 10 feet and held for 15 minutes (312.6). A forced sewer, the discharge line from an ejector or pump (Lesson 9), is tested at a pressure 5 psi greater than the pump rating for 15 minutes (312.7). Storm drain systems inside a building are tested by water or air under 312.2 or 312.3 (312.8), so the ban on air for plastic applies to them too (Lesson 13).

Test gauges (312.1.1)

A test is only as good as the gauge that reads it. Section 312.1.1 sets the finest division the gauge may have, by the pressure being tested.

One gauge seldom serves both a drain air test and a supply test, so a crew usually needs a low-range gauge and a second one for the supply.

Worked example. A three-story clinic has a drain and vent stack that reaches 36 feet above the building drain. Lesson 7 put a 10-foot column at 4.33 psi, so each foot adds 0.433 psi. Filled to the roof opening as one system, the lowest joints carry 36 x 0.433, or 15.6 psi, so the plugs and test fittings at the bottom must be rated for it. Tested in sections, each section needs only its 10-foot minimum, which is 4.33 psi at the bottom of that head. The water supply behind a 65 psi valve is tested at not less than 65 psi with a gauge in 1 psi steps. The ejector's forced sewer, on a pump rated at 20 psi, is tested at 25 psi. The same 5 psi air test on a cast-iron drain would need a gauge in 0.10 psi steps.

Other tests: shower liners and backflow assemblies (312.9, 312.10)

Two more tests turn up on commercial and multifamily jobs. Where a shower floor or receptor is made watertight with a liner, the finished liner is tested with the drain plugged and potable water at least 2 inches deep at the threshold. A temporary threshold is built if none is 2 inches high. The water stays 15 minutes with no sign of leakage (312.9). Backflow prevention assemblies and air gaps get an annual inspection, and the testable assemblies, such as reduced pressure and double check assemblies and pressure vacuum breakers, are tested at installation, immediately after repair or relocation, and at least annually (312.10). For an owner, that annual test belongs on the building's maintenance calendar (Lesson 7).

The inspections (Section 108)

Lesson 1 introduced the three inspections. Here they sit beside the tests. The underground inspection is made after trenches are excavated and bedded and piping is installed, and before any backfill. The rough-in inspection is made after the roof, framing, fireblocking, firestopping, draftstopping and bracing are in place and all sanitary, storm and water distribution piping is roughed in, and before wall or ceiling membranes. The final inspection is made after the building is complete, the fixtures are in place and connected, and the structure is ready for occupancy (108.2). The permit holder schedules each one, notifies the code official when work is ready, and provides access (108.2.2).

Section 312 does not name the inspection at which each test happens, so the last column is normal practice that follows from 108.2.3. That section says work does not go past an inspection point without the code official's approval, and any portion that fails must be corrected and stays uncovered until the code official authorizes it. Read together, the underground piping is tested and inspected before backfill, the drain, vent and supply piping before the walls close, and the fixtures at the end. Section 108.1 keeps the work visible until approved and puts the cost of opening it back up on the permit applicant, not the jurisdiction.

Four smaller rules round out Section 108. The code official may accept reports of approved inspection agencies (108.2.4). For an alternative engineered design plumbing system, the registered design professional or a designated inspector inspects periodically, keeps records, and submits a written final report certifying conformance, and no notice of approval issues until that certification is in (108.3). Testing is not required where the work adds, replaces, alters or relocates no water supply, drainage or vent piping (108.4.1). And work that fails a test or inspection is corrected and resubmitted for inspection and testing (108.4.3). When tests and inspections show compliance, the code official issues the notice of approval (111.1), and no one connects a permitted building to a utility or sewer until the code official authorizes it (112.1). A temporary connection for testing may be authorized (112.2).

Course review

The review below walks the six modules in order and repeats the numbers used most often. It teaches nothing new, and every value carries the same hedges as its lesson. Where a lesson said to check the adopted code, do the same here.

Module 1: Administration and General Regulations (Lessons 1 and 2)

Every job starts with which code binds. Lesson 1's dated check found that Texas cities choose either the Uniform Plumbing Code or the IPC, and that Houston has enforced the 2021 Uniform Plumbing Code with local amendments since early January 2024. This course teaches the IPC as the model and does not teach UPC section numbers. Lesson 2 gathered the rules for every job: marking, protection, trenching, supports and toilet rooms.

Module 2: Fixtures (Lessons 3 and 4)

Lesson 3 counted fixtures: get the occupant load, split it by sex, apply the ratio to each half, round every fraction up, then substitute urinals within the limit. Lesson 4 set them: centerlines, compartments, flow rates and temperature limits. The ratios are Table 403.1 values, and Houston's Uniform Plumbing Code has its own fixture table, so the adopted code gives the actual count.

Module 3: Water Heaters and Water Supply (Lessons 5 to 7)

Lessons 5 to 7 followed the water from the heater and the street main to the fixture. Heaters are about access, relief valves, discharge pipes and pans. The supply is about pressure, separation from the sewer, and keeping the potable water safe from backflow.

Module 4: Sanitary Drainage and Indirect Waste (Lessons 8 to 10)

Lessons 8 to 10 followed the waste out: slope and cleanouts, fixture units and pipe sizes, then indirect waste, traps and interceptors. The dfu tables are the most likely place to carry a wrong number into a real permit, so use the adopted code's tables.

Module 5: Venting (Lessons 11 and 12)

Vents keep pressure swings at a trap seal to 1 inch of water column (901.2). Lesson 11 covered terminals, connections and trap-to-vent distance, and Lesson 12 the venting methods and vent sizes. The height a vent must clear the roof is a blank in the 2021 model text, so it is left to the adopted code, and no lesson in this course quotes a value for it.

Module 6: Storm Drainage, Special Systems, and Review (Lessons 13 and 14)

Lesson 13 turned a rainfall rate and a roof area into gallons per minute, and this lesson proved the finished work with tests and inspections. The rainfall rate is a design value looked up for the site, not a code number, and the constant in the flow equation is worth checking in the adopted code.

The practice exam

The practice exam is the next step. It draws 60 questions, weighted by each topic area's share of the question bank, with a 120-minute time limit. It is a practice tool GCHS built for its own staff development. On an actual project, the locally adopted code, not this course, governs.

Practice questions

Glossary

Head of water

The height of a column of water above a point, which sets the pressure there. A 10-foot head is 4.33 psi, and 312.2 and 312.6 use it as the minimum drain and sewer test.

Water test

A leak test that fills the drain and vent system, or a section of it, with water and holds the pressure not less than 15 minutes (312.2).

Air test

A leak test at 5 psi for drain and vent piping, or at least 50 psi for water supply piping, allowed only for piping other than plastic (312.3, 312.5).

Smoke test

A final test that puts thick smoke into a system whose traps are filled with water, then holds a 1-inch water column for 15 minutes once smoke shows at the roof (312.4).

Forced sewer

A building sewer that is pumped, tested at 5 psi above the pump rating for 15 minutes (312.7).

Underground inspection

The first required inspection, made after the trench is excavated and bedded and the piping is installed, and before any backfill (108.2).

Rough-in inspection

The second required inspection, made after framing and fire protection are in place and all piping is roughed in, and before wall or ceiling membranes (108.2).

Notice of approval

The written approval a code official issues after the prescribed tests and inspections show that the work complies (111.1).