Common leaks
Water heater leaking from the bottom
Water pooling on the floor under a water heater is the leak people worry about most — and for good reason. It's either one of two cheap fixes, or the one leak that means the whole unit has to go. Here's how to tell them apart before you spend a dollar.
Get your specific answer Open the triage with a bottom leak pre-selected — add the age and type for the verdict and cost.The three sources of a bottom leak
Before assuming the worst, trace where the water actually starts. A bottom leak comes from one of three places, in rough order of how cheap they are to fix:
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1. The drain valve
The spigot near the floor can drip from a worn washer or from not being fully closed. It's the cheapest fix — often just replacing the valve, about $150–$300 with a plumber, or a $10–$25 part if you're confident.
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2. The T&P discharge pipe
The pipe running down the side ends near the floor, so water from the relief valve looks like a bottom leak. That's a valve — and pressure — issue, not a failed tank. Never cap the valve.
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3. The tank itself
If the water is genuinely seeping from under the tank body, the steel has rusted through from the inside. A leaking tank can't be sealed or patched — the unit has to be replaced ($700–$1,800 electric, $1,000–$3,000 gas, installed).
How to tell which one it is
Dry everything, put down paper towel, and watch where it gets wet first. Water starting at the drain valve or running down the discharge pipe is a repair. Water appearing under the center of the tank with the valves dry is the tank — especially on a unit past about 10 years old. When it's the tank, keep the heater off and plan for a replacement; a body leak only gets worse.
What to do right now
Shut off the cold water to the heater and cut the gas or power, then contain the water. You don't need to drain the tank for a leak. Walk through the full safe order on the emergency shutoff steps, then use the triage to decide repair or replace and see the replacement cost.
Bottom-leak questions
Why is my water heater leaking from the bottom?
Water pooling under the tank usually comes from one of three places: the drain valve (the spigot near the floor), the T&P discharge pipe running down the side, or the tank itself. The first two are inexpensive repairs. If the water is genuinely seeping from under the tank body, the steel tank has corroded through from the inside — that can't be sealed and the unit has to be replaced. Check the drain valve and discharge pipe first before assuming the worst.
Can a water heater leaking from the bottom be repaired?
If the leak is the drain valve or a connection, yes — those are cheap fixes, roughly $150–$400 with a plumber depending on which fitting it turns out to be. But if the tank body has rusted through, no: a leaking tank cannot be repaired and needs to be replaced. Installed replacement typically runs about $700–$1,800 for an electric tank and $1,000–$3,000 for a gas tank, depending on your region, the brand, and the installation.
How do I turn off the water to a leaking water heater?
Cut the gas or power first, then the water — that order matters, because the hazard is energy near standing water, not the water itself. Then find the cold-water shutoff on the pipe entering the top of the tank (usually the right-hand inlet) and close it: a round handle turns fully clockwise, a lever turns a quarter-turn so it sits across the pipe. If you can't reach it, or it won't close all the way, shut off your home's main water valve instead. Leave the heater switched off for as long as the water is off — an electric element that runs in a tank that has partly emptied burns out within seconds.
Should I repair or replace a leaking water heater?
It comes down to where it's leaking and how old it is. A leaking connection, drain valve, or relief valve on a heater under about 8 years old is usually worth repairing. Past roughly 8–12 years a storage tank is near the end of its service life, so a repair competes with a replacement you'll need soon anyway. A tank leaking from its body is a replacement regardless of age. The triage tool weighs your leak location against the unit's age to give you a specific repair-or-replace call.
How long does a water heater last?
A conventional storage-tank water heater lasts about 8–12 years; a tankless unit often lasts around 20 years with maintenance. Once a tank is past about 12 years, spending money on a repair usually isn't worth it — the tank is likely to fail soon anyway. If you don't know the age, look for the manufacture date encoded in the serial number on the unit's label.