Master Plumber Water Supply and Distribution Questions and Answers

Question 1

A new potable water system has been installed in a commercial building. According to the IPC, which of the following is an acceptable method for disinfection before the system is put into service?

Accepted Answer

Filling the system with a solution containing at least 50 ppm of chlorine and letting it stand for 24 hours.

Answer

The International Plumbing Code (IPC) Section 610 outlines the requirements for disinfecting a potable water system. An approved method involves filling the system with a water/chlorine solution of at least 50 parts per million (ppm) and allowing it to stand for 24 hours. Alternatively, a solution of at least 200 ppm can be used for a 3-hour period.

Question 2

A master plumber is designing a water supply system for a multi-story building. The static pressure from the municipal water main is 95 psi. What is required on the water service pipe near its entrance to the building?

Accepted Answer

A pressure-reducing valve (PRV)

Answer

Most plumbing codes, including the IPC, require a pressure-reducing valve (PRV) to be installed when the static water pressure exceeds 80 psi. This is to protect fixtures and appliances from damage caused by excessive pressure.

Question 3

In a residential hot water supply system, a check valve has been installed on the main water service, creating a closed system. Which of the following is required to mitigate the effects of thermal expansion?

Accepted Answer

An approved and adequately sized expansion tank.

Answer

When a backflow preventer, check valve, or pressure-reducing valve creates a closed system, thermal expansion of heated water can cause a dangerous increase in pressure. Plumbing codes mandate that an approved expansion tank or other device designed for thermal expansion control must be installed to absorb this increased volume and pressure.

Question 4

A master plumber needs to determine the required size for a water service pipe for a new office building. The calculation involves determining the total water supply fixture units (WSFU), the developed length of the piping, and pressure losses. What additional piece of information is critical for this calculation?

Accepted Answer

The available static water pressure at the source.

Answer

To properly size a water service pipe, you must know the starting pressure available from the municipal main or other source. This initial pressure is a key factor in calculating whether sufficient pressure will be available at the most remote fixture after accounting for all pressure losses due to friction, elevation, and equipment.

Question 5

Which of the following scenarios explicitly requires the installation of a water hammer arrestor according to the IPC?

Accepted Answer

On the water supply lines to fixtures with quick-closing valves.

Answer

The IPC Section 604.9 states that a water hammer arrestor shall be installed where quick-closing valves are used. These valves, such as those on clothes washers and dishwashers, can stop the flow of water abruptly, causing a hydraulic shock (water hammer) that can damage pipes and fixtures. The arrestor absorbs this shock.

Master Plumber Exam Practice Test

Master Plumber Exam Practice Test

Master Plumber Water Supply and Distribution Questions and Answers