The Short Answer
If your water heater is leaking, turn off the power and water supply before doing anything else. For gas units, turn the gas valve to “off.” For electric units, flip the breaker. Then shut off the cold water inlet valve on top of the heater. These two steps prevent further damage and keep you safe while you figure out where the leak is coming from.
Step 1: Turn Off the Power
Water and electricity don’t mix. Before you touch anything, kill the power.
- Gas water heater: Find the gas valve on the front of the unit (usually near the bottom). Turn it to the “off” position. Don’t touch the thermostat or any electrical components if you smell gas — leave the house and call your gas company.
- Electric water heater: Go to your electrical panel and flip the breaker labeled “water heater” to off. If breakers aren’t labeled, turn off the main breaker. Don’t stand in pooled water while doing this.
Step 2: Shut Off the Water Supply
Look for the cold water inlet pipe on top of your water heater. There should be a valve — either a gate valve (round handle, turn clockwise) or a ball valve (lever handle, turn 90 degrees). Close it to stop water from flowing into the tank.
If the valve is stuck or broken, shut off the main water supply to your house. The main shutoff is usually near the water meter or where the main line enters your home.
Step 3: Find the Leak
Not all water heater leaks are emergencies. Some are minor fixes. Here’s where to look:
Top of the Tank
Leaks from the top are usually the easiest to fix. Check:
- Cold water inlet and hot water outlet connections: Loose pipe fittings are the most common cause. A wrench can tighten them.
- Anode rod port: If the anode rod fitting is corroded, water seeps out. A plumber can replace the rod and reseal it.
Side of the Tank
- Temperature and pressure (T&P) relief valve: This valve is designed to release water when pressure or temperature gets too high. If it’s dripping, the valve itself might be faulty — or the water pressure in your home is too high. Either way, don’t cap it or plug it. It’s a safety device. Call a plumber.
Bottom of the Tank
- Drain valve: Check if the drain valve at the bottom is fully closed. If it’s dripping even when closed, the valve needs replacing ($10 part).
- The tank itself: Water pooling under the tank with no obvious source means the internal tank has corroded through. This can’t be repaired — the unit needs replacement.
Step 4: Contain the Water
While you wait for a plumber:
- Put towels or a bucket under the leak
- If the leak is significant, connect a garden hose to the drain valve and run it to a floor drain or outside
- Move anything stored near the water heater to prevent water damage — boxes, tools, holiday decorations
- If water is spreading toward electrical outlets or the electrical panel, don’t walk through it — call for help
What NOT to Do
- Don’t ignore it. A small drip becomes a big leak. A 50-gallon tank can flood a room in hours.
- Don’t try to patch a leaking tank. Epoxy, tape, and sealant don’t hold on a corroded steel tank under pressure. It’s a temporary fix that fails.
- Don’t cap the T&P valve. It exists to prevent the tank from over-pressurizing. Blocking it creates a safety hazard.
- Don’t turn the power back on until a plumber says the unit is safe to operate.
When to Call a Plumber vs. DIY
| Situation | DIY? | Call a Plumber? |
|---|---|---|
| Loose pipe fitting on top | Yes — tighten with a wrench | If it still leaks after tightening |
| Dripping drain valve | Maybe — if you’re comfortable | Recommended |
| T&P valve leaking | No | Yes — could indicate pressure issue |
| Water under the tank (no obvious source) | No | Yes — likely tank failure |
| Smell gas near the unit | No — leave the house | Call gas company first, then plumber |
Frequently Asked Questions
Is a leaking water heater dangerous?
A small leak from a pipe fitting isn’t dangerous, but it will get worse. A leaking tank can cause significant water damage and mold growth. And a gas leak near a water heater is a genuine safety emergency — leave the house and call your gas company immediately.
How much does it cost to fix a leaking water heater?
Pipe fitting repairs cost $75 to $200. A new drain valve is $100 to $200 installed. A T&P valve replacement runs $150 to $300. If the tank itself is leaking, you’re looking at full replacement: $600 to $1,400 for a tank unit, $2,500 to $5,500 for tankless.
Can I still use hot water if my water heater is leaking?
If the leak is minor (a dripping fitting) and you’ve confirmed it’s not a gas or electrical hazard, you can use hot water until a plumber arrives. If the tank is actively leaking from the bottom or the T&P valve is releasing water, shut the unit down and don’t use it until it’s inspected.