Where Is a Water Heater Most Likely to Leak? Top 5 Leak Points Explained

If your water heater is dripping, pooling, or making strange hissing sounds, you’re not alone. Water heater leaks are one of the most common household emergencies-and they usually happen in just a few places. Most people panic and assume the whole tank is ruined. But 90% of the time, the leak comes from a simple, fixable part. Knowing exactly where to look can save you hundreds, or even thousands, in replacement costs.

1. The Pressure Relief Valve

This is the most common leak source, and it’s also the easiest to fix. The pressure relief valve sits on top of your water heater. It’s designed to open automatically if pressure builds up too high-like when the water gets too hot or the system can’t vent properly. If it’s leaking constantly, it’s not broken. It’s doing its job, but something else is wrong.

Check if the valve is dripping after you’ve used hot water. If it’s dripping only occasionally, it’s probably just releasing excess pressure from normal use. But if it’s dripping nonstop, the valve might be clogged with mineral deposits, or your water pressure could be too high. Test your home’s water pressure with a simple gauge you can buy at any hardware store. Anything over 80 psi is too high and can stress the valve. Install a pressure-reducing valve if needed.

Replacing the pressure relief valve itself costs under $20 and takes 30 minutes. Just shut off the power and water, drain a few gallons, and unscrew the old one. Make sure the new one matches the thread size and temperature rating (usually 150°F or 210°F).

2. The Anode Rod Corrosion

The anode rod is the unsung hero of your water heater. It’s a metal stick inside the tank that attracts corrosive elements in the water so they don’t eat away at the tank itself. Over time, it sacrifices itself-and when it’s gone, the tank starts rusting from the inside.

If you notice rust-colored water, a rotten egg smell, or a slow drip from the bottom of the tank, the anode rod is likely done. Most rods last 3-5 years, but hard water can kill them in under two. Check yours every two years by removing the cap on top of the heater and using a socket wrench to pull it out. If it’s thinner than a pencil, replace it. A new rod costs $30-$50 and can extend your tank’s life by 5-10 years.

Don’t wait until the tank leaks. Once the tank corrodes, it’s game over. No patch, no sealant, no magic fix. You’ll need a full replacement.

3. The Drain Valve

The drain valve is at the bottom of the water heater. It’s meant to be used once or twice a year to flush out sediment. But if it’s left open, or if the plastic valve is old and cracked, it can start leaking slowly-and you might not notice until you see a puddle on the floor.

Most drain valves are made of cheap plastic. Even if they don’t look damaged, the threads can wear out or the washer inside can harden. Try tightening it with a wrench first. If that doesn’t stop it, replace it. A metal drain valve (brass or stainless steel) costs $15 and lasts decades. Don’t use the plastic ones-they’re the weak link.

Before replacing it, turn off the power and water. Open a hot water faucet in your house to relieve pressure. Then drain a few gallons from the tank to make it easier to remove the valve. Use Teflon tape on the threads of the new valve to ensure a tight seal.

4. The Tank Itself (Rust Holes)

This is the worst-case scenario. If water is leaking from the side or bottom of the tank-especially if it’s rusty, bulging, or covered in white crusty deposits-you’re dealing with internal corrosion. This isn’t a part failure. It’s the tank itself breaking down.

Water heaters last 8-12 years on average. If yours is older than 10 years and leaking from the tank, replacement is your only option. No sealant, no epoxy, no duct tape will fix a corroded tank. Some people try to patch it, but it’s a temporary fix at best. The rust will keep spreading, and you risk a full tank rupture, which can flood your basement or laundry room.

Signs your tank is done: water pooling under the heater, visible rust spots, loud popping or rumbling noises (from sediment buildup), and water that smells or looks dirty. If you see any of these, start shopping for a new unit. Don’t wait for it to burst.

5. Pipe Connections and Fittings

Leaks can also come from where the pipes connect to the water heater-especially the hot water outlet and cold water inlet. These connections are under constant pressure and temperature changes. Over time, the seals loosen, or the pipes corrode.

Check the joints with your hand or a dry paper towel. If it’s damp, trace the water back to the source. Sometimes it’s just a loose fitting. Tighten it gently with a wrench-don’t over-torque. If the pipe itself is corroded (greenish or flaky), you’ll need to replace that section. Copper pipes last 20-30 years. If your home is older than that, the pipes might be the real problem.

Also watch for flex connectors. These rubber hoses connecting the heater to the pipes are a common failure point. They can crack, harden, or swell. Replace them every 5-7 years with braided stainless steel ones. They’re stronger, more durable, and less likely to burst.

What to Do When You Find a Leak

Step 1: Turn off the power. For electric heaters, flip the breaker. For gas, turn the dial to “Pilot” or “Off.”

Step 2: Shut off the cold water supply. Look for the valve on the pipe coming into the top of the heater. Turn it clockwise until it stops.

Step 3: Drain the tank slightly. Open a hot water faucet in your house to let air in. Then open the drain valve and let a few gallons out. This reduces pressure and makes repairs safer.

Step 4: Identify the source. Use a flashlight and dry cloth to wipe down the tank and connections. Watch for where the moisture returns fastest.

Step 5: Fix it or replace it. If it’s a valve, replace it. If it’s the anode rod, replace it. If it’s the tank, call a pro and start budgeting for a new unit.

Prevention Tips to Avoid Future Leaks

• Flush your tank every 6-12 months to remove sediment. This reduces strain on the heating elements and prevents corrosion.
• Test your water pressure annually. Keep it between 40-60 psi.
• Install a water softener if you have hard water. Minerals accelerate anode rod and tank corrosion.
• Replace the anode rod every 3-5 years. It’s cheap insurance.
• Upgrade to a tankless water heater if you’re replacing your unit. They last 20+ years and don’t have tanks to rust.

Most leaks aren’t disasters. They’re warnings. Catch them early, and you avoid a flooded basement, mold, or a $1,500 emergency replacement. Know your water heater’s weak spots-and check them before they check you.