306A Water Supply Systems 4

Question 1

When using the fixture unit method to size water supply piping, what does the conversion to litres per second account for?

Accepted Answer

The probability that not all fixtures will be used simultaneously

Answer

The fixture unit method uses probability theory to account for the fact that in most buildings, not all fixtures operate at the same time. This diversity factor allows smaller pipe sizes than if every fixture were assumed to run simultaneously.

Question 2

What is the standard test pressure for a water supply system in a residential building?

Accepted Answer

150 psi (1034 kPa) for a minimum of 2 hours

Answer

The water supply system is typically tested at 100 psi (690 kPa) or 1.5 times the working pressure, whichever is greater, and held for a minimum of 2 hours with no visible leaks or pressure drop.

Question 3

What is the purpose of an expansion tank on a closed-loop domestic hot water system?

Accepted Answer

To absorb the volume increase when water is heated and the system has a backflow preventer

Answer

When a backflow preventer creates a closed system, heated water expands with nowhere to go, causing dangerous pressure increases. An expansion tank absorbs this thermal expansion safely.

Question 4

What is the minimum size of an individual fixture supply pipe for a lavatory?

Accepted Answer

⅜ inch

Answer

A ⅜-inch supply pipe is the minimum size for a lavatory faucet, providing adequate flow for handwashing while conserving water.

Question 5

What is the effect of installing a water softener on the hot water supply only?

Accepted Answer

Reduced scale buildup in the water heater and hot water pipes

Answer

Installing a softener on the hot water supply reduces scale buildup (calcium and magnesium deposits) in the water heater and hot water piping, improving efficiency and extending equipment life.

Red Seal Plumber 306A Practice Test

Red Seal Plumber 306A Practice Test

306A Water Supply Systems 4