Water heaters: Georgia Journeyman Plumber Practice Questions

What safety device must every storage-type water heater have?

A T&P relief valve (or separate temperature and pressure valves) opens before the tank can overheat or overpressure and explode.

At what maximum temperature must a water heater's temperature relief function open?

The temperature relief is set at no more than 210°F, below the 212°F boiling point at atmospheric pressure, so the stored water cannot flash to steam.

What is the highest pressure setting allowed for a water heater's relief valve?

The pressure relief may not be set above the working pressure marked on the heater (typically 150 psi).

Where must the temperature-sensing element of a T&P relief valve be?

The hottest water rises to the top, so the sensing element must be in the top 6 inches of the tank to react in time.

What size must the T&P relief valve discharge pipe be?

The discharge pipe is full size (at least the valve outlet size) all the way, so the valve can relieve its rated flow.

May a shutoff valve be installed in a T&P relief valve discharge pipe?

A valve in the discharge line could be closed and disable the relief valve, so none is allowed.

Which T&P discharge pipe installation violates the codes?

The discharge pipe must drain by gravity with no traps or upward runs; a rise creates a trap that holds water, can freeze and slows relief.

Why must the end of a T&P discharge pipe NOT be threaded?

A threaded end invites a cap or plug that would block the relief path. The codes require a plain end.

Under the IPC, a T&P discharge pipe ending inside the building over the floor must end no higher than:

The IPC lets the discharge end at the floor, a pan, a waste receptor or outdoors, terminating no more than 6 inches above the floor or receptor so the hot discharge does not spray people.

Which material may NOT be used for a T&P relief valve discharge pipe?

Discharge piping must handle 210°F water; PVC is rated for cold water only. Copper, CPVC, PEX and galvanized steel are listed options.

Under the IPC, a water heater is fed from the bottom (the cold water enters at the bottom of the tank). What extra device is required?

If the supply is lost, a bottom-fed tank can be siphoned and collapse; a vacuum relief valve (ANSI Z21.22) lets air in.

Where is a shutoff valve required at a water heater?

Both codes require a shutoff on the cold supply to the water heater so it can be isolated for service.

Under the IPC, what fitting must be installed at the bottom of a tank-type water heater?

A drain valve at the bottom lets sediment be flushed and the tank emptied for replacement.

When is a drain pan required under a storage water heater?

Both codes require a pan where leakage would damage the building, with a drain piped to an approved location.

What is the minimum size of a water heater pan drain?

Pan drains are at least 3/4 inch and run to an indirect waste receptor, floor drain or outdoors.