Why Your Water Heater Is Leaking (and How to Stop It)

Water on the floor around a water heater is easy to ignore, but it rarely fixes itself. Some leaks are minor and cheap to stop, such as a drain valve that isn’t fully closed or a loose fitting. Others mean the tank itself is failing and needs to be replaced before it lets go. This guide walks you through making the area safe, finding exactly where the water is coming from, what you can reasonably fix yourself, and when it is time to call a licensed plumber.

General information only. Electrical, gas, and refrigerant work can be dangerous and in many states requires a licensed contractor. When in doubt, call a licensed pro.

First, Make It Safe

If water is actively pooling, deal with safety before you start investigating.

Turn off the energy source. On an electric heater, switch off its breaker at the electrical panel. On a gas heater, turn the gas control knob to “Pilot” or “Off.” If you smell gas (a rotten-egg odor), don’t touch any switches; leave the house and call your gas utility from outside.
Shut off the cold water supply. The shutoff valve is usually on the cold-water pipe at the top of the heater. Turning it off stops the tank from refilling, which slows or stops most leaks.
Keep water away from electrical parts. Move stored items, outlets, and extension cords away from the puddle, and put down towels or a shallow pan.
Don’t let an electric tank run empty with the power on. Heating elements that run without water around them burn out quickly. Always cut the power before you drain anything.

Water in a heater is often set to 120Â°F or hotter, so wear gloves and be careful around valves and drain lines that may release hot water.

Make Sure It’s Actually the Water Heater

Before blaming the heater, rule out other sources nearby. Water heaters often share space with other equipment that can drip.

Condensation on gas models. When a gas heater fills with cold water, moisture from the burner’s exhaust can condense on the cold tank and drip onto the burner. You may hear sizzling. This usually stops once the water heats up. If it continues all day, have it checked.
An AC or furnace in the same closet. Air conditioners and high-efficiency furnaces produce condensate water. A clogged drain line or cracked pan can leak onto the floor next to the heater. See our guide on why an AC leaks water inside.
Nearby plumbing. Water softeners, filters, washing machine hoses, and pipes overhead can all drip down onto or beside the heater.

Dry the area completely, then lay paper towels around the base and on top of the heater. Check them every 15 to 30 minutes. The first wet spot is usually your best clue.

Where Water Heaters Leak and What Each Leak Means

Top of the heater: inlet and outlet connections

The hot and cold pipes connect at the top. Leaks here usually come from loose or worn flexible connectors, corroded dielectric unions or nipples, or a failing cold-water shutoff valve. Mineral crust or green or white buildup on a fitting is a sign of a slow, long-running seep. Water from a top leak can run down inside the insulation and show up at the bottom, so always check the top before assuming the tank has failed.

The temperature and pressure (T&P) relief valve

The T&P valve is a safety device on the side or top of the tank with a pipe running down toward the floor. It opens to release water if the temperature or pressure inside the tank gets too high. If water is coming from that discharge pipe, the valve is either doing its job (pressure or temperature really is too high) or it is worn and no longer seals.

Common causes are household water pressure that’s too high, thermal expansion in a “closed” plumbing system (a check valve, backflow preventer, or pressure-reducing valve stops expanding hot water from pushing back into the main), a thermostat set too high, or an old valve. Never cap, plug, or remove the T&P discharge pipe. It protects against a dangerous tank failure.

Drain valve near the bottom

The drain valve (a spigot for flushing the tank) can drip if it isn’t fully closed, if sediment is keeping it from seating, or if the valve itself is worn. Many factory drain valves are plastic and become brittle with age.

The bottom of the tank or under the outer jacket

If you have ruled out the fittings, the T&P valve, and the drain valve, and water is coming from under the heater or from beneath its outer metal jacket, the inner tank has probably rusted through. Rust-colored water, rust streaks at the base, or a damp, rusty burner area are typical signs. A leaking tank can’t be repaired; it needs to be replaced.

Anode rod port

The anode rod screws into the top of the tank. A leak around its hex head usually means the threads or seal need attention, which is a job best done with the tank drained.

Fixes You Can Usually Handle Yourself

These jobs suit homeowners who are comfortable with basic tools. Turn off power and water first.

Snug up a loose connection. Use two wrenches (one to hold the fitting, one to turn) and tighten gently. Overtightening can crack fittings or damage threads. If a flexible connector is kinked, corroded, or still drips, replace it with one of the same size and type.
Close and cap the drain valve. Make sure the valve is fully closed. If it still drips, a brass garden-hose cap with a rubber washer screwed onto the outlet often stops a minor drip until the valve can be replaced.
Flush sediment from a sticking drain valve. Briefly opening the valve with a hose attached can clear grit that keeps it from sealing. Be aware that an old plastic valve may not close properly afterward, so have a cap ready.
Check your water pressure. A simple pressure gauge that screws onto an outdoor spigot or the heater’s drain valve shows your house pressure. Many homes run between about 40 and 60 PSI. Plumbing codes commonly call for a pressure-reducing valve when pressure exceeds 80 PSI.
Lower the thermostat. About 120Â°F is a common recommendation for comfort, efficiency, and scald safety. A setting that’s too high can contribute to T&P valve discharge.
Replace a worn drain valve or T&P valve. Both are standard parts, but the tank usually has to be partly or fully drained. A new T&P valve must match the rating on the heater’s label. If you aren’t comfortable with that, this is a quick job for a plumber.

How to drain the tank if the tank is leaking

If the tank itself is leaking, draining it limits damage while you arrange a replacement. With the power and cold supply off, connect a garden hose to the drain valve, run it to a floor drain or outside to a lower point, open a hot-water faucet somewhere in the house to let air in, and then open the drain valve. Remember the water may be very hot.

When to Call a Licensed Plumber

Water is coming from the tank body, seams, or underneath the jacket.
The T&P valve keeps discharging after you’ve confirmed normal pressure and temperature.
Fittings are badly corroded or seized and could break if you force them.
You see scorch marks, smell gas, notice burner or venting problems, or see water near wiring or the burner compartment.
You need an expansion tank, a pressure-reducing valve, or a new water heater installed.

Replacing a water heater involves gas or electrical connections, venting for gas models, a T&P discharge line, and often a local permit and inspection. It is generally a job for a licensed plumber.

Repair or Replace?

Valves, connectors, and fittings are inexpensive parts, and fixing them is usually worthwhile even on an older heater. Replacement makes sense when the tank itself leaks, when there is significant rust at the base, or when the heater is near the end of its typical life. Standard tank heaters commonly last around 8 to 12 years, depending on water quality and maintenance. The manufacture date is usually encoded in the serial number on the label, and the manufacturer’s website can help you decode it. If a heater that age needs repeated repairs, it’s often smarter to plan a replacement than to wait for a failure.

How to Prevent Future Leaks

Flush the tank about once a year, or more often with hard water, to reduce sediment buildup.
Inspect the anode rod every few years. It corrodes on purpose to protect the tank. Once it’s mostly gone, the tank starts to corrode.
Keep the temperature around 120Â°F unless you have a specific reason to run it hotter.
Install or check an expansion tank if you have a closed plumbing system. Its air charge should be set to match your house water pressure.
Use a drain pan with a drain line if the heater sits where a leak would damage floors or ceilings. A battery-powered water leak alarm on the floor gives early warning.
Look at the heater every few months. Check the top fittings, the T&P discharge pipe, and the floor around the base.

Frequently Asked Questions

Why is my water heater leaking from the bottom?

Check the drain valve first, then look for water running down from the top fittings or the T&P discharge pipe. If none of those are the source and the water is coming from under the tank or jacket, the inner tank is most likely corroded and needs to be replaced.

Can I still use a leaking water heater?

If the leak is a small drip from a fitting or the drain valve, you may be able to keep using the heater until it’s repaired, as long as the area stays dry and safe. If the tank itself is leaking, turn off the power or gas and the cold supply and arrange a replacement. A failing tank can get worse suddenly.

Why is my T&P valve dripping?

Usually because of high water pressure, thermal expansion in a closed system, a thermostat set too high, or a worn valve. Check pressure and temperature first. If those are normal and it still drips, the valve likely needs replacing.

Is a leaking water heater an emergency?

A minor drip isn’t an emergency, but it should be fixed soon. Steady leaking, water near electrical or gas components, or a leaking tank should be treated as urgent. Shut off power and water and call a plumber.