Journeyman Plumber ExamWater Supply SystemsEasy
A plumber is inspecting a residential water heater installation. The water heater is installed in a garage and is equipped with a temperature and pressure (T&P) relief valve. To comply with plumbing codes, the discharge pipe from this T&P valve must terminate in which of the following manners?
- AInto the combustion air intake duct of the water heater.
- BInto an indirect waste receptor, air gaped, and visible to the occupants.
- CInto a sealed drain line that connects directly to the potable water supply.
- DDirectly to the exterior of the building, terminating no more than 6 inches above grade.
Show answer & explanationAnswer & explanation
Correct answer: B. Into an indirect waste receptor, air gaped, and visible to the occupants.
The discharge pipe from a T&P relief valve must terminate to an indirect waste receptor with an air gap, or to the exterior, to prevent contamination of the potable water system and to safely discharge high-temperature, high-pressure water while being visible for inspection.
Why the other options are wrong
- A. Discharging into a combustion air intake duct is extremely dangerous, posing a risk of fire, explosion, or carbon monoxide poisoning.
- C. Connecting directly to the potable water supply would create a cross-connection hazard.
- D. While discharge to the exterior is often allowed, the 'no more than 6 inches above grade' is not universally correct and doesn't specify an air gap or visibility.
T&P Valve Discharge Termination
The safe and code-compliant method for directing the discharge from a water heater's temperature and pressure relief valve.
- Must prevent cross-connection
- Must be visible
- Typically to indirect waste or exterior
- Requires air gap
Memory trick: T&P discharge: Gap it wide, so no backflow can hide!