Free Master Plumber Plumbing System Design & Sizing Questions and Answers

Question 1

A master plumber is designing a natural gas piping system for a commercial building with multiple appliances.
The longest pipe run from the meter to the furthest appliance is 150 feet.
The total connected load is 450,000 BTU/hr.
Using the longest length method and a typical sizing table for 0.5 psi gas pressure with a 0.5-inch water column pressure drop, what is the required pipe size for the main trunk line leaving the meter?

Accepted Answer

2-inch

Answer

1-inch

Answer

1 1/4-inch

Answer

1 1/2-inch

Question 2

When designing a storm drainage system for a 10,000 square foot roof, which of the following is the primary factor in determining the required size of the horizontal storm drains and vertical leaders according to most model plumbing codes?

Accepted Answer

The maximum projected roof area.

Answer

The number of roof drains installed.

Answer

The height of the building.

Answer

The material of the roofing membrane.

Question 3

A new 80-gallon commercial water heater is being installed in a closed-loop potable water system with an incoming city water pressure of 65 psi. To accommodate thermal expansion, an expansion tank is required. What is the first and most critical step in correctly sizing this expansion tank?

Accepted Answer

Calculating the total system volume, including all piping.

Answer

Determining the static fill pressure of the system at the tank's location.

Answer

Setting the pressure relief valve to its maximum setting.

Answer

Selecting the tank with the smallest physical footprint.

Question 4

In a multi-story building, a plumbing system is designed using a combination waste and vent system for a stack of floor drains. Which of the following is a key requirement for this type of system under the International Plumbing Code (IPC)?

Accepted Answer

The waste pipe must be oversized to allow for air circulation.

Answer

The pipe must be sized one size smaller than a standard drainage pipe.

Answer

The system can receive waste from toilets and urinals.

Answer

Air admittance valves are required at each fixture.

Question 5

A sewage ejector pump is required for a basement bathroom group (water closet, lavatory, and shower) that is below the public sewer line. According to common plumbing code standards, what is the minimum size for the sump pit diameter and the discharge pipe for a non-grinder pump serving a water closet?

Accepted Answer

18-inch diameter pit, 2-inch discharge

Answer

12-inch diameter pit, 1 1/2-inch discharge

Answer

24-inch diameter pit, 1 1/2-inch discharge

Answer

16-inch diameter pit, 3-inch discharge

Question 6

A master plumber is sizing the main water distribution pipe for a small office building using the Water Supply Fixture Unit (WSFU) method. The total load is 50 WSFU (flush valve system), the static pressure is 70 psi, and the developed length to the most remote fixture is 200 feet. Using a standard IPC sizing table for Type L copper pipe, what is the critical calculation needed before selecting a pipe size from the chart?

Accepted Answer

The pressure available for friction loss.

Answer

The total number of bends in the piping system.

Answer

The average temperature of the supply water.

Answer

The elevation of the water main in the street.