Plumbing & Mechanical Systems Flashcards

What is the minimum slope required for horizontal drainage piping with a 3-inch diameter per the IPC?

Answer: 1/8 inch per foot

The IPC requires 3-inch horizontal drainage pipes to slope at a minimum of 1/8 inch per foot toward the point of discharge.

A pressure-reducing valve (PRV) is required when the water service pressure exceeds which threshold?

Answer: 80 psi

Per the IPC, a PRV must be installed when the water supply pressure exceeds 80 psi to protect fixtures and piping.

Which type of trap is prohibited under most modern plumbing codes?

Answer: S-trap

S-traps are prohibited because they can self-siphon, losing the water seal that prevents sewer gases from entering the building.

During a hydrostatic pressure test on new water supply piping, what is the minimum test pressure and duration required by the IPC?

Answer: 100 psi for 15 minutes

The IPC requires new water supply systems to be tested at 100 psi for a minimum of 15 minutes without leaking.

What is the primary function of a backflow preventer in a plumbing system?

Answer: Prevent contaminated water from entering the potable supply

A backflow preventer stops contaminated or non-potable water from reversing flow and entering the clean water supply due to back-pressure or back-siphonage.

An inspector notices that a sanitary tee is installed horizontally in a drainage system. This is:

Answer: A code violation requiring correction

Sanitary tees must not be used in a horizontal position because they cause turbulence and solids buildup; a wye fitting must be used instead.

What is the purpose of the air gap required at a plumbing fixture indirect waste connection?

Answer: Protect against backflow contamination

An air gap provides a physical break between the waste outlet and the flood level rim of the receptor, preventing backflow contamination of potable water.