2.4 Required Tests: Water, Air, and Backflow Assembly Testing

Whose job the test is

IPC 312.1 assigns the work: the permit holder makes the applicable tests, gives reasonable advance notice to the code official when the plumbing is ready, and furnishes the equipment, material, power and labor for the inspection and test. The permit holder — not the inspector — is responsible for determining that the work will withstand the prescribed pressure.

That has a practical consequence Colorado codifies separately. Board Rule 1.6(B)(3) requires the installation to be "complete and under test" before you request the inspection, and Rule 1.6(B)(5)(a) authorizes a reinspection fee when the job is not ready and an extra trip is required. An inspector who arrives to a zeroed gauge does not troubleshoot your system; the inspection fails and the reinspection fee attaches.

IPC 312.1 also says systems are tested "with either water or, for piping systems other than plastic, by air."

Test gauges — IPC 312.1.1

The code specifies gauge resolution, and exam items do ask for it:

A DWV air test at 5 psi therefore demands a 0.10 psi gauge. A 100-pound shop gauge reading in 5-pound steps is not an acceptable instrument for that test, which is exactly why a slow leak can pass unnoticed on the wrong gauge.

The DWV tests

312.2 Drainage and vent water test

Apply water to the drainage system in its entirety or in sections.

• Entire system: close all openings tightly except the highest, and fill to the point of overflow.
• In sections: plug each opening except the highest opening of the section under test; no section may be tested with less than a 10-foot head of water.
• Successive sections: not less than the upper 10 feet of the preceding section must be re-tested, so that no joint or pipe in the building — except the uppermost 10 feet — has been subjected to less than a 10-foot head.
• Hold for not less than 15 minutes. The system shall then be tight at all points.

A 10-foot head is 4.33 psi at the base (10 ft / 2.31 ft per psi).

312.3 Drainage and vent air test

Plastic piping shall not be tested using air. An air test shall be made by forcing air into the system until there is a uniform gauge pressure of 5 psi, or sufficient to balance a 10-inch column of mercury. This pressure shall be held for a test period of not less than 15 minutes.

Adjustments for ambient temperature change or gasket seating must be made before the 15-minute test period begins — not during it.

Colorado field note (not exam-scored): Board Rule 1.2(E)(1)(m) deletes the sentence "Plastic piping shall not be tested using air." In Colorado you may air test PVC and ABS DWV, which is why the 5 psi air test is the everyday Colorado rough-in test. On the exam, the model-code answer is that plastic shall not be air tested. Keep the two answers in separate mental drawers.

312.4 Drainage and vent final test

The final test of the completed drainage and vent system is visual and in sufficient detail to determine code compliance. Where a smoke test is used, fill all traps with water, introduce thick pungent smoke from one or more smoke machines, and when smoke appears at the stack openings on the roof, close those openings and hold a pressure equivalent to a 1-inch water column for not less than 15 minutes.

Colorado field note: Board Rule 1.2(E)(1)(n) deletes 312.4 in its entirety, and Rule 1.2(E)(1)(l) removes the matching final-test sentence from 312.1.

The supply-side and sewer tests

Notice the constant: 15 minutes is the holding period for nearly every test in Section 312. The variable is the pressure.

Colorado field notes: Rule 1.2(E)(1)(o) removes the "other than plastic" limitation from 312.5, so plastic water piping may be air tested in Colorado. Rule 1.2(E)(1)(p) deletes 312.9 shower liner test from the Colorado Plumbing Code.

Backflow assembly inspection and testing

IPC 312.10.1 requires annual inspections of all backflow prevention assemblies and air gaps to determine whether the assemblies are operable and the air gaps exist.

IPC 312.10.2 requires reduced pressure principle, double check, pressure vacuum breaker, reduced pressure detector fire protection, double check detector fire protection and spill-resistant vacuum breaker assemblies, plus hose connection backflow preventers, to be tested:

1. at the time of installation,
2. immediately after repairs or relocation, and
3. at least annually.

Testing follows ASSE 5013, 5015, 5020, 5047, 5048, 5052, 5056, CSA B64.10 or CSA B64.10.1, and test gauges must comply with ASSE 1064.

Colorado field note: Board Rule 1.2(E)(1)(q) rewrites 312.10.2 to require the test be performed by a certified cross-connection control technician — a person holding a valid Backflow Prevention Assembly Tester certification from ASSE, the American Backflow Prevention Association, or another Board-recognized agency (Rule 1.2(D)(8)(a)) — and adds the USC Foundation for Cross-Connection Control and Hydraulic Research 10th Edition Manual as an approved procedure.

Worked example: staging a three-story rough-in

A three-story building has a DWV stack 34 feet from the building drain to the roof terminal.

1. Underground (Colorado inspection category 1): the below-grade DWV is capped and filled to produce at least a 10-foot head, or air tested at 5 psi with a 0.10 psi gauge. Hold 15 minutes.
2. Section 1 of the stack, floors 1-2: plug all openings except the highest of that section; fill so the section sees at least a 10-foot head.
3. Section 2, floors 2-3: re-test the upper 10 feet of section 1 along with section 2, so no joint below the top 10 feet of the building ever sees less than a 10-foot head.
4. Water supply at rough-in: pressurize to working pressure with potable water — or, on metallic piping under the model code, 50 psi of air — and hold 15 minutes.
5. Request the inspection only once every system is complete and holding, with plans on site for a commercial job, ladders provided and the address visible from the street.