Home Safety
Every tank water heater has a temperature and pressure (T&P) relief valve — a spring-loaded safety that opens automatically if the tank's temperature or pressure ever runs away. It's the part that stands between a failed thermostat and a catastrophic tank failure. It needs three things: to exist, to work, and to never, ever be capped.
Water expands when heated — and if a thermostat sticks and the burner won't shut off, the tank becomes a sealed vessel with rising pressure and superheated water. The T&P valve is the engineered failure point: it opens at set limits and dumps hot water safely through its discharge pipe instead of letting pressure build toward tank failure. It's a simple mechanical part doing one critical job.
The valve's outlet must be piped correctly to do its job safely.
Occasional dripping usually means one of three things: system water pressure is too high (a failing pressure regulator — common in our area's high-pressure zones), thermal expansion has nowhere to go (closed systems need an expansion tank), or the valve itself is aging out. Each has a proper fix. The improper fix — capping the valve or plugging the discharge — converts a drip into a pressure vessel problem. It's the single most dangerous shortcut in residential plumbing.
The valve has a test lever: lifted briefly (with something to catch hot water), it should discharge and then reseat cleanly. If it won't open, or won't stop dripping after a test, it's done — replacement is inexpensive. We test the T&P, check system pressure, and verify the discharge piping on every water heater maintenance visit; if your tank hasn't had that in years, it's a five-minute check that covers the highest-consequence failure the appliance has.
Very likely — that's the T&P discharge pipe doing its job or telling you about pressure. Occasional small discharges after heavy hot-water use suggest thermal expansion; steady dripping points at high pressure or a tired valve. Either way it's worth a check: the causes are fixable and the valve is cheap to replace.
No — never. Capping the T&P valve removes your water heater's only overpressure protection while the underlying problem continues. If the dripping bothers you, that's the signal to get the actual cause fixed (pressure regulator, expansion tank, or valve replacement), not to silence the messenger.
Residential code targets a maximum of 80 psi, and most homes are comfortable in the 50–70 range. Parts of LA & OC sit on high-pressure mains where a working pressure regulator is essential — when regulators fail (they age like everything else), pressure climbs and every fixture, hose, and valve in the house feels it, T&P included. A gauge check takes minutes.
Last reviewed: 2026-07-22
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