Slow drip from the discharge pipe
A few drops every few minutes or a damp floor near the relief valve drain tube.
Start here: Dry the area completely, then watch whether the drip starts during a heating cycle or continues all day.
Water heater leak troubleshooting
Water Heater Pressure Relief Valve Leaking
Direct answer: If the pressure relief valve on your water heater is dripping or running, do not assume the valve itself is bad. Most of the time the valve is doing its job because tank temperature is too high, house water pressure is too high, or the valve got fouled and will not reseat cleanly.
Most likely: The most common real-world causes are a valve that has debris on the seat, water that is set too hot, or pressure building in the tank when the water heats up.
First make sure the water is actually coming from the temperature and pressure relief valve and not from a fitting above it. A few drops after a full heating cycle is different from a steady drip all day. Reality check: a relief valve is supposed to leak when pressure or temperature gets unsafe. Common wrong move: replacing the valve before checking temperature and supply pressure.
Don’t start with: Do not start by capping the discharge pipe, plugging the opening, or cranking on the valve repeatedly. That turns a warning leak into a safety problem fast.
If the discharge pipe is warm and wet right after the burner or elements run,check for overheating or pressure buildup before buying a valve.
If water is tracking down from a fitting above the valve body,fix that upper leak first because the relief valve may be innocent.
Last reviewed: 2026-04-17
What the leak pattern is telling you
Steady trickle or small stream
Water is actively running from the relief valve pipe and does not stop on its own.
Start here: Shut off power to an electric water heater or set a gas control to pilot if you know how, then stop using hot water and check for overheating or excessive pressure.
Leak seems to be at the valve but source is unclear
The valve body is wet, but fittings, nipples, or venting above it may also be damp.
Start here: Use a flashlight and paper towel to trace the highest wet point before touching the valve.
Leak happens only after heavy hot water use
The valve drips after showers, laundry, or dishwasher runs, then dries up later.
Start here: That pattern points more toward pressure expansion or high temperature than a cracked tank.
Most likely causes
1. Debris or mineral scale keeping the water heater T&P relief valve from reseating
A valve can spit once, then keep dripping because grit or scale is stuck on the seat. This is especially common on older tanks or after the valve has been tested manually.
Quick check: Place a cup under the discharge pipe, dry the valve body, and see if the leak is a light persistent drip rather than a strong release.
2. Water heater temperature set too high
If the tank is overheating, the relief valve opens to dump hot water and pressure. You may also notice scalding hot water at faucets.
Quick check: Run hot water at a nearby tap for a minute and check the temperature carefully with a thermometer. If it is unusually hot, back the setting down and monitor.
3. Excess house water pressure or thermal expansion
When incoming pressure is already high, normal heating can push the tank over the relief point. This often shows up after long heating cycles or heavy hot water use.
Quick check: Notice whether the leak is worse after the tank reheats from a big draw, then eases off later.
4. A worn or damaged water heater T&P relief valve
If temperature and pressure seem normal and the valve still leaks from the outlet or around the threads, the valve itself may be spent.
Quick check: After the tank cools slightly and the area is dry, confirm the water is coming from the valve outlet or body and not from a fitting above it.
Step-by-step fix
Step 1: Confirm the relief valve is really the leak source
Water from a pipe joint, vent connection, or fitting above the valve often runs down and makes the relief valve look guilty.
- Turn off power to the electric water heater at the breaker, or for a gas unit turn the control to pilot if you are comfortable doing that.
- Dry the relief valve, discharge pipe, and the fittings above it with a towel.
- Use a flashlight and a dry paper towel to check the highest point where fresh moisture appears.
- Look for water beading at the relief valve outlet, around the valve threads, or from a fitting above the valve.
Next move: If you find the leak starts above the relief valve, you have ruled out the valve itself and can focus on that upper fitting or connection. If the first fresh water shows up at the relief valve outlet or body, keep going. The valve is either responding to a real pressure or temperature problem, or it is not sealing anymore.
What to conclude: You want the true source before you touch parts. A top-down leak and a relief discharge are two different jobs.
Stop if:
- Water is spraying rather than dripping.
- You see active leaking at gas piping, vent parts, or electrical connections.
- The tank shell itself is leaking or rusted through.
Step 2: Separate a one-time spit from an active safety release
A few drops after a heating cycle can come from a valve that did not reseat cleanly. A steady flow points more toward overheating or pressure buildup and needs faster action.
- Place a container under the discharge pipe if you can do it safely without blocking the pipe.
- Leave the area dry and check it over the next heating cycle or after normal hot water use.
- Feel the discharge pipe carefully near the end only if it is safe to do so; it may be hot.
- Note whether the leak is just a few drops, a repeating drip, or a steady trickle.
Next move: If it only drips briefly after reheating and then stops, pressure expansion or a dirty valve seat is more likely than a catastrophic tank problem. If it runs steadily or the water is very hot, treat it as an active safety release and move to temperature and pressure checks right away.
What to conclude: The leak pattern tells you whether you are chasing a nuisance drip or a condition the valve is actively trying to relieve.
Step 3: Check whether the water heater is running too hot
Overheating is one of the main reasons a relief valve opens, and it is more important to rule out than the valve itself.
- At a nearby sink or tub, run hot water for about a minute so you are testing tank water, not cooled water sitting in the pipe.
- Use a thermometer to check the hot water temperature carefully.
- If the water is hotter than expected, lower the water heater temperature setting one step and give the tank time to stabilize.
- Over the next day, watch whether the relief valve drip slows or stops after the lower setting.
Next move: If the leaking stops after lowering the temperature, the valve was likely responding to overheating rather than failing on its own. If the water temperature seems normal and the valve still leaks, pressure buildup or a worn valve becomes more likely.
Step 4: Look for pressure buildup clues before replacing the valve
A relief valve that leaks mostly after reheating often points to high incoming pressure or thermal expansion in the plumbing, not just a bad valve.
- Notice whether the leak is worst after showers, laundry, or other heavy hot water use when the tank has to recover.
- If you already know the home has high water pressure or a pressure reducing valve on the main line, keep that in mind because expansion problems are more common there.
- Do not cap or restrict the discharge pipe to stop the drip.
- If the leak only happens during reheating and the water temperature is normal, plan on having house pressure and expansion conditions checked if you are not equipped to test them.
Next move: If the pattern clearly matches reheating only, you have a strong clue that the valve is reacting to pressure conditions rather than just wearing out. If the valve drips all the time even with normal temperature and no clear pressure pattern, the valve itself is a stronger suspect.
Step 5: Replace the relief valve only when the diagnosis supports it
Once you have ruled out a leak from above, obvious overheating, and a clear pressure-only pattern, a worn or fouled relief valve is a reasonable repair path.
- Buy a replacement water heater T&P relief valve only after matching the valve style and ratings to your existing water heater requirements.
- Shut off the water heater power source and water supply, and relieve pressure before any valve removal.
- If the old valve has been dripping lightly for a while, inspect the opening and discharge path for mineral buildup as the valve comes out.
- Install the new water heater T&P relief valve correctly, reconnect the discharge pipe, refill the tank fully, and restore power only after the tank is full.
- If a new valve still leaks under normal temperature settings, stop replacing parts and have the water pressure and expansion setup checked.
A good result: If the new valve stays dry through several heating cycles, the old valve was likely not sealing properly anymore.
If not: If the new valve also discharges, the problem is not the valve. The tank is seeing excessive temperature or pressure and needs further diagnosis.
What to conclude: A replacement valve is the right fix only after the easy lookalikes are off the table. If the leak returns, the system condition is the real issue.
Replacement Parts
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FAQ
Why is my water heater pressure relief valve leaking only sometimes?
That usually points to a condition that shows up during reheating, not a constant plumbing leak. Common examples are water set too hot, high incoming pressure, or pressure expansion after heavy hot water use.
Can I just replace the pressure relief valve and be done?
Sometimes, yes, but only after you rule out overheating and pressure buildup. If the new valve leaks too, the valve was not the real problem.
Is a dripping relief valve dangerous?
It can be. A few drops are less urgent than a steady hot discharge, but any relief valve leak deserves attention because it may be warning about unsafe temperature or pressure in the tank.
Should I open and close the valve handle to flush it out?
Not as a first move on an older leaking valve. Sometimes that clears debris, but it also commonly leaves the valve unable to reseat and turns a small drip into a bigger one.
What if the leak is actually coming from above the valve?
Then the relief valve is not the problem. Water from a fitting, nipple, or connection above it can run down and drip off the valve or discharge pipe, so always trace the highest wet point first.
Why does the valve leak after showers or laundry?
That pattern often shows up when the tank reheats after a big hot water draw. If temperature is normal, pressure expansion in the plumbing is a strong suspect.