Plumber exam: Water heaters

Key points

• The temperature and pressure relief valve protects the tank from overpressure and overheating.
• The T&P discharge pipe must run full size and not be capped.
• Expansion tanks absorb thermal expansion in closed systems.
• The anode rod slows tank corrosion.
• Higher storage temperatures control Legionella, while mixing valves prevent scalding.

Study tip

If a T&P valve drips in a closed system, think thermal expansion before replacing the valve.

Try these

1. A T&P valve discharge line should:

   1. Be capped
   2. Be reduced in size
   3. Run full size to an approved point
   4. Run uphill
   Show answer

   C. Run full size to an approved point It must not be restricted.

2. An expansion tank is needed when:

   1. The system is open
   2. A backflow device makes it closed
   3. The heater is electric
   4. The tank is small
   Show answer

   B. A backflow device makes it closed Closed systems trap expansion.

3. The anode rod:

   1. Heats water
   2. Prevents tank corrosion
   3. Measures pressure
   4. Vents gas
   Show answer

   B. Prevents tank corrosion It corrodes in place of the tank.

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