Water heaters

Water heater temperature and pressure relief valve is dripping

The T&P valve is a safety device that releases water if pressure or temperature gets too high, and occasional dripping usually means it's doing its job or needs replacing, not that it should be capped off.

Difficulty
Moderate
Time
20–40 minutes to assess
DIY cost
$15–$40
Pro cost
$150–$300

Symptoms

  • Water dripping steadily from the pipe running down the side of the tank
  • Dripping happens more after hot water use
  • Valve may have a mineral crust around it
  • No error codes if the unit has a display

Likely causes

  • CommonExcess pressure in the plumbing system, often from a closed system with no expansion tankHomes with a check valve or pressure regulator can build excess pressure without an expansion tank to absorb it.
  • CommonThermostat set too high, causing excess pressure from overheated waterWater heated well above 120–140°F expands more and can trigger the valve.
  • CommonWorn or failing T&P valve that no longer seals properlyValves can wear out and leak even at normal pressure and temperature.
  • PossibleSediment or debris preventing the valve from reseatingMineral buildup on the valve seat can keep it from closing fully.

What to do

  1. Check the thermostat setting and lower it to around 120°F if it's set higher.
  2. Do not cap, plug, or remove the discharge pipe under any circumstances, since this valve is a critical safety device.
  3. If your system has a check valve or pressure-reducing valve on the main supply, ask a plumber whether an expansion tank is needed.
  4. Try lifting the valve's test lever briefly (if accessible and you're comfortable) to let it clear and reseat; expect a burst of hot water.
  5. If dripping continues steadily after lowering the thermostat and testing the lever, the valve itself likely needs replacing.
  6. Track how often and how much it drips so a plumber can judge whether it's a pressure issue or a worn valve.

Tools and parts

  • None required for inspection
T&P relief valveSearch: “water heater temperature pressure relief valve”
Thermal expansion tankSearch: “water heater expansion tank”

When to call a pro

If the valve keeps dripping after checking temperature and pressure causes, have a plumber replace the valve or add an expansion tank as needed.

Safety

Use caution

Never cap, plug, or disable the T&P valve; doing so removes a critical safety device that prevents the tank from becoming dangerously over-pressurized.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.