InterNACHI - International Association of Certified Home Inspectors Plumbing Systems Inspection Questions and Answers

Question 1

An inspector, while evaluating a home's drain, waste, and vent (DWV) system, hears a distinct gurgling sound from the bathtub drain immediately after flushing a nearby toilet. Both fixtures appear to drain adequately otherwise. What is the most probable cause of this gurgling sound?

Accepted Answer

A partial blockage or inadequate plumbing vent.

Answer

Gurgling sounds from adjacent fixtures are a classic sign of a venting problem. When the toilet is flushed, a large volume of water rushing down the drain creates negative pressure. If the vent stack is blocked or improperly installed, the system will draw air from the easiest source, which is often through the P-trap of a nearby fixture like a bathtub, causing the water in the trap to gurgle.

Question 2

What is the primary safety purpose of the Temperature and Pressure Relief (TPR) valve installed on a residential water heater?

Accepted Answer

To prevent dangerous pressure or temperature buildup by discharging water.

Answer

The TPR valve is a critical safety device designed to open automatically if either the temperature (typically >210°F) or the pressure (typically >150 psi) inside the tank exceeds safe limits. By discharging water, it prevents a potentially catastrophic explosion.

Question 3

During an inspection of a home built in 1988, an inspector identifies flexible, gray plastic water supply pipes stamped with "PB2110." This piping material is known as:

Accepted Answer

Polybutylene (PB)

Answer

Polybutylene (PB) is a type of plastic piping, often gray and marked with the code "PB2110," that was used extensively from the late 1970s to the mid-1990s. It is known to degrade when exposed to oxidants in public water supplies, becoming brittle and failing without warning, which led to class-action lawsuits and its removal from building codes.

Question 4

While inspecting a home's exterior, you observe a garden hose attached to a hose bibb with the other end of the hose lying submerged in a small, decorative pond. This situation represents a significant risk known as a:

Accepted Answer

Cross-connection with a potential for back-siphonage

Answer

This is a classic example of a cross-connection, where the potable water supply is potentially connected to a source of contamination. If a pressure drop occurs in the main supply line (e.g., due to a water main break or firefighting), contaminated water from the pond could be siphoned back into the home's drinking water.

Question 5

According to common plumbing codes, a P-trap is installed at each fixture to block sewer gases from entering the home. What is the generally accepted minimum and maximum water seal depth for a standard P-trap?

Accepted Answer

2 inches minimum, 4 inches maximum

Answer

Most plumbing codes specify that a standard fixture P-trap must maintain a water seal of at least 2 inches to be effective against sewer gas and no more than 4 inches. A seal deeper than 4 inches can slow drainage and make it more likely to trap debris, while a seal less than 2 inches is more susceptible to evaporation or being siphoned out.

(InterNACHI) International Association of Certified Home Inspectors Practice Test

(InterNACHI) International Association of Certified Home Inspectors Practice Test

InterNACHI - International Association of Certified Home Inspectors Plumbing Systems Inspection Questions and Answers