Water Heater Leaking? What to Do Now, Causes by Location and Repair Costs

Last updated: October 2026

If your water heater is leaking, shut off the power or gas, close the cold water supply valve on top of the tank, and then work out where the water is coming from. Leaks from the top (pipe connections) or the drain valve are usually cheap repairs, but water coming from the bottom of the tank itself almost always means the tank has corroded through and needs to be replaced. A leak from the temperature and pressure (T&P) relief valve can be a sign of dangerous pressure or temperature, so it should never be ignored or plugged.

This guide walks you through the exact shutoff steps, how to diagnose a leak by its location, what each repair typically costs, and when a leaking water heater is a genuine emergency.

Quick reference: water heater leak by location

Is a leaking water heater dangerous?

Most leaks are not immediately dangerous to people, but some are, and all of them can cause expensive water damage if left alone. The risks fall into four groups:

• Gas leaks. A gas water heater that is leaking water can also have a damaged gas line, flue or burner assembly. If you smell rotten eggs or sulfur, that is a gas leak, not a water leak, and it takes priority over everything else (see the warning below).
• Electrical shock. Electric water heaters run on 240-volt circuits. Water pooling around an electric unit, its junction box or a nearby outlet creates a shock risk. Do not stand in water and touch the heater or its wiring.
• Scalding. Water inside the tank can be 120°F to 140°F or hotter, and much hotter if the thermostat has failed. The U.S. Consumer Product Safety Commission (CPSC) notes water at 140°F can cause a third-degree burn in about 6 seconds, and at 150°F in about 2 seconds.
• Pressure. A T&P relief valve that is discharging is doing its job: releasing excess pressure or heat. If the valve has been capped, plugged or has seized, a tank can fail violently. Never cap a relief valve or its discharge pipe.

What to do if your water heater is leaking: step by step

Work through these steps in order. They take about 10 minutes and will stop most leaks from getting worse while you figure out the cause.

1. Check for a gas smell first. If you smell gas, stop and follow the warning above.
2. Cut the energy supply.
   • Electric: Switch off the water heater’s double-pole breaker (usually labeled “water heater” or “WH,” often 30 amps) at the main panel. If you have to stand in water to reach the heater’s own disconnect, use the breaker panel instead.
   • Gas: Turn the gas control knob on the front of the heater to “OFF” (or “Pilot” if you plan to restart soon). For a full shutoff, turn the handle on the gas supply line so it sits perpendicular (crosswise) to the pipe.
3. Shut off the cold water supply. Find the valve on the cold water inlet pipe at the top of the tank (usually marked with blue or on the right side as you face the unit) and turn it clockwise until it stops, or a quarter turn for a lever-style ball valve. If that valve won’t close or there isn’t one, close the main water shutoff for the house.
4. Relieve the pressure. Open a hot water faucet somewhere in the house. This drops the pressure in the tank and can slow or stop a leak from fittings or the relief valve.
5. Contain the water. Move valuables, boxes and rugs away. Put down towels or use a wet/dry vac. If the heater is in an attic, closet or upper floor, check the ceiling below.
6. Dry the tank and find the source. Wipe the tank, pipes and valves completely dry with a towel, wait 10–20 minutes, and look for where water reappears first. Water runs down, so a bottom leak may start at the top.
7. Decide whether to drain the tank. If water is coming from the tank body itself (not a fitting or valve), the tank will keep leaking until it is empty. Attach a garden hose to the drain valve, run it to a floor drain or outside, and open the valve. Be careful: the water will be hot.
8. Call a plumber if the leak is from the tank, the T&P valve keeps discharging, you can’t shut off the water, or the unit is gas and you’re not comfortable working around it.

Why is my water heater leaking? Causes by location

The location of the water is the single best clue to the cause, and to whether you’re looking at a repair or a replacement. Start at the top of the heater and work down.

Rule out condensation first

Not every puddle is a leak. Manufacturers including A. O. Smith note that condensation can form when cold incoming water (especially in winter) cools the tank, and on gas units when the burner fires and moisture in the combustion gases condenses on the cold tank or flue. This “sweating” can drip onto the burner and even make a sizzling sound. Condensation is typically temporary and stops once the water in the tank heats up. If the floor is dry after the tank has been at temperature for a few hours with no large hot water draws, condensation is the likely culprit. If water keeps appearing, it’s a real leak.

Water heater leaking from the top

Leaks at the top are the most common and usually the cheapest to fix. Check these spots:

• Cold inlet and hot outlet connections. The pipes connect to the tank with threaded nipples, often through flexible connectors. Thermal expansion and contraction can loosen them over time, and dissimilar metals (copper on steel) can corrode. A slightly loose compression nut may just need a gentle snug-up with a wrench. Don’t overtighten; that can crack fittings and make things worse. A corroded nipple or flex line needs to be replaced.
• Cold water shutoff valve. The packing nut behind the valve handle can drip. Tightening the packing nut an eighth to a quarter turn often stops it; otherwise the valve needs replacing.
• Anode rod port. The anode rod screws into the top of the tank (on some models it’s combined with the hot outlet). If the fitting has corroded or the seal has failed, water seeps out around it. Replacing the anode rod with new thread sealant usually fixes it.
• T&P valve (top-mounted). On some heaters the relief valve is on top. See the relief valve section below.
• Tank top seam. If water is seeping from under the top cover itself rather than from a fitting, the tank may be failing at the top. That’s a replacement.

Water heater leaking from the relief valve

The T&P (temperature and pressure) relief valve is the brass valve with a lever, usually on the side or top of the tank, with a pipe running down toward the floor. Residential valves are commonly rated to open at 150 psi or 210°F; the exact rating is printed on the valve’s tag. A relief valve leaking or discharging points to one of these causes:

• Thermal expansion. Water expands as it heats. If your home has a pressure-reducing valve, a check valve or a backflow preventer on the main line (common with newer water meters), that extra volume has nowhere to go and pressure spikes during every heating cycle. The usual fix is a properly sized and pre-charged thermal expansion tank, which many local codes require on these “closed” systems.
• High street pressure. Household water pressure above 80 psi is generally too high, and plumbing codes typically require a pressure-reducing valve above that level. A $10–$15 hose-bib pressure gauge will tell you your pressure in a minute.
• Overheating. A thermostat set too high or a failed thermostat can push water toward the valve’s temperature limit. If the water at your taps is dangerously hot or you hear the tank boiling or rumbling, turn off the power or gas and call a plumber.
• A worn or dirty valve. Sediment or mineral scale can stop the valve from seating properly after it opens, so it drips constantly. Replacing the valve is a modest repair (about $20 for the part, up to around $200 with a plumber, according to Angi).

Water heater leaking from the bottom

This is the scenario most homeowners search for, and it has two very different outcomes depending on exactly where the water is coming from.

1. The drain valve. The drain valve sits near the bottom front of the tank and looks like a hose spigot. If it’s dripping from the spout, it may not be fully closed, or debris from sediment may be stopping it from sealing. Try closing it firmly by hand. Many factory valves are plastic and can crack or wear. A temporary fix is a brass garden hose cap screwed onto the outlet; the real fix is replacing the valve with a brass one, which requires draining the tank. This is a small repair.

2. The relief valve discharge pipe. The T&P discharge pipe ends near the floor, so a dripping relief valve can look like a “bottom” leak. Check the end of the pipe. If it’s wet, go back to the relief valve section.

3. The tank itself. If water is coming from under the tank, from the burner compartment on a gas unit, or from beneath the jacket (outer shell) on an electric unit, and you’ve ruled out the drain valve, discharge pipe and condensation, the inner steel tank has almost certainly corroded through. Tanks are protected by a glass lining and a sacrificial anode rod, but once the anode is used up, corrosion attacks the steel. Sediment buildup on the bottom accelerates this, particularly on gas units where the burner heats the tank bottom. A corroded tank cannot be repaired. The leak will get worse, sometimes suddenly. Drain the tank and plan a replacement.

Leaking from the electrical access panels (electric)

Electric tanks have one or two access panels covering the heating elements and thermostats. Water behind these panels can come from a leaking element gasket, which is repairable when the element is replaced. If it’s coming from the tank wall around the element, the tank is failing. Always turn off the breaker before removing an access panel and confirm it’s dead with a non-contact voltage tester.

Tankless water heater leaking

Tankless leaks are usually at the water connections, isolation valves, pressure relief valve or heat exchanger. On condensing models, a clogged or disconnected condensate line can also look like a leak. A leaking heat exchanger is a major repair; check the warranty, which is often longer than a tank’s. See our guide to tankless water heater cost.

Water heater leak repair costs

Prices vary by region, unit type and whether you need an emergency call-out. The ranges below are typical national figures from cost guides such as Angi and This Old House; they’re a guide, not a quote.

Plumber labor typically runs $50 to $150 per hour, and many plumbers charge a flat service-call fee. After-hours, weekend and holiday calls cost more. For a detailed breakdown of individual repair prices, see our water heater repair cost guide.

Repair or replace a leaking water heater?

Use the leak location and the heater’s age together to make the call.

Repair it if:

• The leak is from a fitting, valve, anode port or heating element gasket, and the tank itself is dry.
• The heater is less than about 8 years old and otherwise working well.
• The relief valve is discharging because of pressure that an expansion tank or pressure-reducing valve will solve.
• The repair is a small fraction of replacement cost.

Replace it if:

• The tank itself is leaking. This is the one situation with no repair option.
• The heater is 10 years or older (most tank heaters last roughly 8 to 12 years in practice; the U.S. Department of Energy cites about 10 to 15). See our water heater lifespan guide for how to find your unit’s age from the serial number.
• You see rust in the hot water, rust on the tank bottom, or heavy corrosion on the fittings.
• The repair would cost more than about half the price of a new heater on an older unit. This “50% rule” is a common industry rule of thumb, not a hard law.

If you’re replacing anyway, it’s a good moment to reconsider size and type. Our guides cover water heater replacement cost, 50-gallon replacement costs, gas vs electric, tankless vs tank, heat pump water heaters and what size water heater you need. Labor and code upgrades (expansion tank, drain pan, earthquake straps in some states, venting) can add significantly to the price; see installation labor costs.

When is a leaking water heater an emergency?

Call a plumber (or your gas utility) right away if any of these apply:

• You smell gas or rotten eggs near the heater.
• Water is near the electrical panel, outlets or the heater’s wiring and you can’t safely shut off the breaker.
• The T&P valve is spraying or discharging continuously, or the tank is making loud banging, boiling or hissing sounds.
• You can’t stop the water: the cold water shutoff won’t close and you can’t find the main shutoff.
• The heater is in an attic, upstairs closet or finished space where a leak will damage ceilings and floors.
• Water is pouring rather than dripping from the bottom of the tank.
• The tank is bulging or visibly deformed.

A slow drip from a fitting or drain valve can usually wait for a scheduled appointment once the water is off. A drip from the tank itself is urgent: tank leaks get worse, not better.

How to prevent water heater leaks

1. Flush the tank once a year (every six months with hard water) to remove sediment that corrodes the tank bottom. Here’s how to flush a water heater safely.
2. Check the anode rod every few years and replace it before it’s down to the core wire.
3. Test the T&P valve once a year by lifting the lever briefly, with a bucket under the discharge pipe. If it won’t reseat and keeps dripping, replace it.
4. Check your water pressure and install an expansion tank if you have a closed system.
5. Keep the thermostat at about 120°F, the setting recommended by the DOE and CPSC for energy savings and scald prevention.
6. Install a drain pan and a leak alarm (or an automatic shutoff valve) so a leak becomes a minor cleanup, not a disaster.

FAQs

Why is my water heater leaking from the bottom?

The most common causes are a drain valve that isn’t fully closed or has worn out, a dripping T&P relief valve whose discharge pipe ends near the floor, condensation, or a corroded tank. Check the drain valve and discharge pipe first. If both are dry and water is coming from under the tank, the tank has likely rusted through and needs replacing.

Is a leaking water heater dangerous?

It can be. A small fitting leak is mainly a water-damage risk, but leaks can also create shock hazards around electric units and scalding risks from very hot water. A relief valve that discharges repeatedly signals high pressure or temperature. If you smell gas, leave the home and call your gas utility or 911 from outside.

Can I still use my water heater if it’s leaking?

It’s best not to. If the leak is from a fitting or valve, you can sometimes use the heater after a proper repair. If the tank itself is leaking, shut off the water and energy supply and drain it, because the leak will worsen and could release a large amount of water.

How long can a water heater leak before it bursts?

There’s no reliable timeline. A pinhole leak in a corroded tank may drip for days or weeks, or the weakened steel can fail suddenly. Because you can’t predict it, treat any tank leak as a reason to replace the unit promptly.

Can a leaking water heater be repaired?

Yes, if the leak is from a fitting, the drain valve, the relief valve, the anode port or an element gasket. No, if the leak is from the tank itself. Corrosion inside the tank can’t be patched in a way that is safe or lasting.

Why is my water heater leaking from the pressure relief valve?

Usually because of high pressure from thermal expansion in a closed system, high incoming water pressure (above about 80 psi), water that’s too hot, or a worn valve that won’t reseat. An expansion tank, a pressure-reducing valve or a new relief valve typically solves it. Never plug the valve.

Why is my water heater leaking from the top?

Most top leaks come from loose or corroded inlet and outlet connections, a dripping shutoff valve, the anode rod fitting, or a top-mounted relief valve. These are usually inexpensive repairs. Water seeping from beneath the top cover with no fitting involved can indicate a failing tank.

Is it normal for a water heater to have water underneath it?

A little moisture from condensation can be normal, particularly on gas units when cold water enters the tank. It should stop once the water is hot. Ongoing puddles are not normal and point to a leak.

How much does it cost to fix a leaking water heater?

Simple fixes like tightening fittings cost little or nothing. Replacing a relief valve runs up to about $200, an expansion tank $100–$400, and the average water heater repair is around $616 nationally. If the tank is leaking, expect to pay roughly $1,200 to $3,500 or more for a replacement.

Does homeowners insurance cover a leaking water heater?

Policies usually cover sudden water damage to your home caused by the leak, but not the cost of the water heater itself, since that’s considered wear and tear. Long-term leaks you didn’t address may not be covered. Check your policy and document the damage.