Water Heaters
Water Heaters covers installation safety: relief protection, discharge piping, drain pans, thermal expansion, combustion air, venting, and seismic restraint. P1 questions frequently test the temperature and pressure relief valve because improper discharge piping is both common and dangerous.
Relief valve and discharge
Storage water heaters require a temperature and pressure relief valve set to open at not more than 210°F and 150 psi. The discharge pipe must remain full size, run by gravity, have no valve or trap, and terminate not more than 6 inches above the floor or outside under IPC 504.6. It must not be capped or reduced.
Pans, expansion, and location
A water heater in a location where leakage could cause damage needs a drain pan with a drain. In a closed system, thermal expansion can raise pressure; an expansion tank or other approved means is needed. Water heaters in seismic areas require strapping, typically two straps, with the lower strap in the lower third and the upper strap in the upper third.
Combustion air and venting
Fuel-fired heaters need combustion air and venting per the code and manufacturer’s instructions. A drafthood or direct-vent arrangement must be installed correctly, with clearances to combustibles maintained. Appliances must be accessible for service and relief valve inspection.
Worked example
A 3/4-inch T&P valve is piped with a 1/2-inch copper discharge line that runs through a trap and terminates 12 inches above the floor. Three defects exist: the pipe is reduced, it is trapped, and it terminates too high. The discharge must be full size, gravity-drained without a trap, and terminate not more than 6 inches above the floor.
Traps that cost marks
Capping the discharge, installing a shutoff valve on it, or reducing its size are frequent wrong answers. Candidates also forget expansion control on a closed system and omit seismic strapping where required.