General regulations, materials, joints & testing: Maine Journeyman Plumber Practice Questions

Which job is normally exempt from a plumbing permit under the model codes?

Both codes exempt minor repairs such as stopping leaks and clearing stoppages when no piping is replaced or relocated. New fixtures, water heaters and rerouted piping need a permit.

When must the rough-in inspection of drainage, vent and water piping be made?

Rough-in work must be inspected and tested before it is covered by walls, ceilings or backfill. Work covered too early can be ordered uncovered.

Who furnishes the equipment, material and labor for the required plumbing tests?

The codes put the cost and work of testing on the permit holder or installer. The inspector witnesses the test.

For a water test of a drain and vent system tested in sections, each section must be tested with at least what head of water?

Both codes require at least a 10-ft head of water on every joint except the top 10 ft of the system, held for at least 15 minutes.

How long must the water test on a drain, waste and vent (DWV) system be held?

The water must stay in the system for at least 15 minutes with no leaks or drop in level.

When an air test is used on a DWV rough-in, what pressure is applied and for how long?

The DWV air test is a uniform 5 psi (or enough to balance 10 inches of mercury) held for 15 minutes. Both codes forbid air testing plastic piping.

A finished water distribution system is tested with water. What test pressure do the codes require?

Water supply piping is tested with water at no less than its working pressure, using water from a potable source. Some local amendments set a higher fixed minimum.

An air test may replace the water test on metallic water supply piping. What minimum air pressure is used?

Both codes allow a 50 psi air test instead of the water test, but never on plastic piping, because compressed air in plastic can shatter it.

How often must a reduced pressure principle backflow assembly normally be tested?

Testable assemblies (RPZ, double check, pressure vacuum breaker) are tested when installed, after repair or relocation and at least annually, by a certified tester.

Use 0.433 psi per foot of water. What pressure does a 10-ft head of water put on the lowest joint of a section under test?

Each foot of water column adds 0.433 psi, so a 10-ft head gives 4.33 psi.

A 3-story DWV stack is filled with water to the top of a vent 28 ft above the building drain. Use 0.433 psi per foot. What pressure acts on the building drain joints?

The bottom joints carry the whole column of water. Testing the full height at once puts more pressure on the lowest joints than the 10-ft minimum.

Use 0.433 psi per foot of water. A 5 psi air test equals about how many feet of water head?

Divide pressure by 0.433 to get feet of head. That is why 5 psi of air is a little stricter than a 10-ft water head.

Water, soil and waste pipes installed where they could freeze, such as outside walls or unheated attics, must be:

Both codes require piping exposed to freezing temperatures to be protected by insulation, heat or both. Plastic pipe can still freeze and split.

A trench for a building sewer runs parallel to a footing. Which rule do the codes apply?

Digging inside the 45-degree bearing plane of a footing can undermine the foundation, so both codes keep parallel trenches out of it.

How must backfill be placed over plastic or metal pipe in a trench?

Backfill must be free of rocks, broken concrete and frozen chunks, placed in layers and compacted so the pipe is evenly supported and not damaged.