TPR valve
The temperature and pressure relief valve on a water heater, which discharges if temperature or pressure exceeds safe limits.
What is TPR valve?
A water heater without functioning relief is a genuine explosion hazard, which puts the TPR valve among the small set of findings inspectors treat as safety-critical. The common defects are consistent and easy to spot: no discharge pipe at all, a pipe that terminates too high above the floor, a pipe reduced in diameter, a pipe that runs uphill, threads or a cap on the discharge end, or a pipe made of an unapproved material. General guidance is a full-size pipe running downhill and terminating six inches or less above the floor with no threads, so that a discharge is visible and cannot be capped. Corrosion at the valve suggests it has been weeping.