Journeyman Plumber ExamWater Supply SystemsMedium
A residential water heater is equipped with a temperature and pressure (T&P) relief valve. The discharge pipe from this valve should terminate in a specific manner according to plumbing codes. Which of the following describes the correct termination for a T&P relief valve discharge pipe?
- ATo an indirect waste receptor, air gap, and visible discharge.
- BInto the combustion air intake of the water heater.
- CThrough an exterior wall, terminating below a window.
- DDirectly into a closed drainage system with a trap.
Show answer & explanationAnswer & explanation
Correct answer: A. To an indirect waste receptor, air gap, and visible discharge.
The T&P relief valve discharge pipe must terminate to an indirect waste receptor with an air gap. This setup prevents any potential back-siphonage or back-pressure from the drainage system contaminating the potable water supply while allowing safe, visible discharge of hot water and steam, indicating a potential problem with the water heater.
Why the other options are wrong
- B. Terminating into the combustion air intake is extremely dangerous, as it could extinguish the flame or introduce water into the combustion chamber, leading to fire or carbon monoxide hazards.
- C. While an exterior termination is sometimes used, it should not be below a window or in a location where it could cause injury or property damage, and it still requires an air gap for safety.
- D. Direct connection to a closed drainage system with a trap is a cross-connection hazard, as it could allow sewer gases or contaminants to enter the potable water system through the T&P valve.
T&P Valve Discharge Termination
The proper method for routing the discharge from a temperature and pressure relief valve to safely release hot water or steam, typically to an indirect waste receptor with an air gap.
- Prevents backflow into the potable water system.
- Must be visible to indicate valve activation.
- Avoids injury and property damage.
Memory trick: T&P discharge: visible, indirect, air gap, no back-contaminant trap.