T&P Relief Valve Dripping or Spraying? Read This First

What the T&P valve does

Every storage water heater must have a self-closing temperature and pressure relief valve in the top of the tank. Under Indiana’s plumbing code (section 504.5), it opens at no more than 210°F, or at the tank’s rated pressure up to 150 psi. Its discharge pipe has to run by gravity, without traps, to within 6 inches of the floor or a drain, where you can see it (section 504.6). That pipe is why a relief-valve leak often looks like a puddle at the base of the heater.

Three common reasons it leaks

1. Pressure is actually too high

When water heats, it expands. If the home has a check valve or a pressure-reducing valve at the meter, that extra volume has nowhere to go and pressure spikes during each heating cycle. The relief valve opens to protect the tank. Fixing the valve alone won’t stop this; the system may need a thermal expansion tank or a pressure adjustment.

2. Temperature is set too high, or a control has failed

A thermostat set very high, or a stuck control or element, can push water toward the valve’s temperature limit. CPSC recommends 120°F for scald safety. Water near the relief point is far hotter and can burn badly.

3. The valve is worn or fouled

With Westfield water averaging about 22 grains per gallon of hardness, mineral deposits can build up on the valve seat so it no longer seals after opening. Older valves simply wear out. A valve that keeps weeping at normal temperature and pressure usually needs replacing.

What to tell the provider

• Does it drip constantly, only during heating, or did it spray once?
• Is the heater gas or electric, and roughly how old?
• Do you know of a pressure-reducing valve or an expansion tank on the system?
• Where does the discharge pipe end, and is it intact?