Water Heater Leaking From the Bottom? Causes and What to Do

First: limit the damage

1. Turn off the energy source. Gas: turn the control knob to "off" or "pilot". Electric: switch off the water heater's breaker. Never heat an empty or draining tank.
2. Close the cold water inlet valve on the pipe entering the top of the heater. This stops the tank refilling. If that valve won't close, use the main house shutoff.
3. Move anything stored around the heater and start mopping. If it's in a garage, a squeegee toward the garage door works well.
4. Leave the tank full for now unless it's pouring out. Draining it isn't urgent once the supply is off, and water coming out of the bottom is under less pressure with the inlet closed.

Find the real source

Dry everything with towels, then watch for a few minutes. Paper towels laid around the base show fresh drips clearly. Work through these in order.

1. The drain valve (most common repairable cause)

The drain valve is the small spigot near the bottom of the tank where you'd connect a hose.

• Dripping from the spout: the valve isn't fully closed or its seal is worn. Try gently closing it by hand. A brass garden-hose cap screwed onto the outlet is a common temporary stop.
• Leaking around the valve body where it enters the tank: the threads or the plastic valve itself have failed. A plumber can usually replace the valve.
• Why it happens here: sediment builds up at the bottom of the tank and can keep the valve from seating. That's especially relevant in McKinney (see the local note below).

2. The T&P relief valve and its discharge pipe

The temperature and pressure relief valve is on the top or upper side of the tank, with a pipe running down toward the floor or into a drain pan. Water that appears at the bottom often came from this pipe.

• Water dripping from the end of the discharge pipe means the valve is opening. That can be a worn valve, or it can be a real warning that the tank is getting too hot or pressure is too high.
• Don't cap or plug the discharge pipe. The valve is a safety device that prevents the tank from rupturing.
• A plumber should check the thermostat setting, the valve, and the home's water pressure. Homes with a pressure-reducing valve or a check valve on the supply may need a thermal expansion tank.

3. Condensation

Gas water heaters can produce condensation, especially when filled with cold water or run hard in winter. It shows up as small amounts of water near the burner area and may stop once the tank is hot. If the "leak" appears only after a big draw of hot water and dries up within an hour or so, condensation is likely. Persistent water isn't condensation.

4. Plumbing above the heater

Check the hot and cold connections, flexible connectors and any shutoff valve on top of the tank. Water running down the outside of the tank collects at the base and looks like a bottom leak. Loose fittings and worn connectors are repairable.

5. The tank itself

If the water is coming from:

• the seam at the bottom of the tank,
• underneath the heater with nothing wet above it, or
• through the insulation or jacket, often with rust-colored staining,

then the steel inner tank has corroded through. Tanks can't be patched. The leak will get worse, sometimes slowly, sometimes suddenly. Plan for water heater replacement.

Repair or replace?

• Drain valve dripping or leaking at the threads: usually repairable.
• T&P valve discharging: find the cause first; often repairable.
• Loose or worn connections on top: usually repairable.
• Condensation on a gas unit: monitor it; no repair needed.
• Water from the tank body, seam or insulation: replace the heater.

Other factors a plumber will weigh: the heater's age (the manufacture date is encoded in the serial number on the label), whether it is still under warranty, and whether it also has performance problems. If you're also dealing with lukewarm water, see water heater not heating.

What not to do

• Don't keep the heater running while you "wait and see" if the tank is leaking. It won't seal itself.
• Don't plug the T&P discharge pipe or remove the valve.
• Don't over-tighten a plastic drain valve. It cracks easily.
• Don't try to drain a tank full of heavy sediment through a failing valve without a plan. The valve can break open and won't close again.

DIY vs calling a plumber

Reasonable DIY: shutting off the heater and water, cleaning up, identifying the source, capping a dripping drain spout, and tightening a visibly loose fitting by hand.

Call a licensed plumber for: replacing the drain valve or T&P valve, anything involving the gas line or burner, pressure and expansion problems, and any tank replacement. In McKinney, replacing a water heater requires a City permit, according to the City's home repairs permit page. A licensed plumber pulls the permit and arranges the inspection.

What to tell the plumber

• Gas or electric, tank size (on the label) and approximate age
• Exactly where the water is coming from, with a photo if possible
• Whether you've shut off the water and power or gas
• Where the heater is: garage, attic, closet. Attic heaters leaking into ceilings are more urgent.

Our water heater repair page covers repairable problems in more detail.

Prevention

• Flush the tank to remove sediment. Many manufacturers suggest once a year. With McKinney's hardness, don't skip it.
• Check the anode rod every few years. It's the part that corrodes instead of the tank. Replacing it before it's used up can extend tank life.
• Test the T&P valve as the manufacturer describes, carefully, with a bucket under the discharge.
• Make sure the heater has a drain pan with a working drain line, especially in attics and closets. Texas plumbing code requires a pan in many installations.
• Keep the area around the base clear so you notice drips early.