Your water heater is leaking. Here's what to do.

Water at a heater comes from one of five places, and which one decides whether this is a cheap fix or a new unit: the cold and hot connections at the top, the T&P relief valve or its discharge pipe, the drain valve near the floor, a supply valve or flexible line, or the tank body itself. The first four are fittings, and fittings are usually repairable. Water seeping from under the tank body is the exception — the steel tank has corroded through from the inside, and that can't be sealed. Find the exact spot before you spend anything: the triage tool turns the leak's location, the unit's age, and tank-versus-tankless into a specific cause and a repair-or-replace call.

It can be. The water itself is usually just a mess, but a water heater combines standing water with gas or electricity and stores water hot enough to scald (120 °F or more). Before anything else, cut the energy — turn a gas unit's control knob to Off, or switch an electric unit's breaker off at the panel — then shut off the cold water to the heater. If you smell gas (a rotten-egg smell), don't touch any switch: leave the house and call your gas company or 911 from outside.

Almost certainly not. An explosion takes two safety systems failing at the same time: the thermostat or high-limit switch has to fail and let the water superheat, and the T&P relief valve has to be blocked, seized, or capped so the pressure can't escape. Industry safety guidance treats that combination as highly unlikely on a modern heater, and a leak on its own doesn't cause it — a T&P valve that's discharging is the safety system doing its job. The one thing that genuinely raises the risk is capping or plugging a dripping T&P valve, so never do that. If it's discharging, lower the thermostat and have a plumber find out why it opened.

Follow the safe order: (1) cut the gas or power to the heater; (2) close the cold-water shutoff on the pipe entering the top of the tank, or your home's main water valve if you can't reach it; (3) contain the water — you don't need to drain the tank for a leak; (4) leave the T&P relief valve alone if that's where the leak is; and (5) call a licensed plumber if it doesn't stop, the tank is leaking from its body, or you're unsure. Enter your leak's location in the triage tool for the specific cause and next step.

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.

Once you've closed the cold-water shutoff, you have whatever hot water is left in the tank and no more, so plan on cold showers until it's fixed. Before that, it depends on the leak. If water is coming from the T&P relief valve, don't run hot water at all until a plumber has looked at it — that valve only opens when temperature or pressure is too high. Stay away from the unit if the leak has reached wiring, a plug, or the burner area, and remember the water can be scalding at 120 °F or more. A small drip at a fitting on an otherwise healthy heater is the one case where short-term use is usually fine.

It's better not to. Even a slow leak can worsen quickly, waste water, and cause water damage or mold, and a leak near gas or electrical connections is a hazard. The safe move is to shut off the water and the gas or power, contain the leak, and get it looked at before running it again. If it's leaking from the tank body, keep it off — that unit needs replacing.

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.

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.

The T&P valve is a safety device that opens to release water when the tank's temperature climbs past about 210 °F or its pressure past about 150 psi. A drip means either the valve is worn out, or it's correctly relieving excess pressure or heat caused by a too-high thermostat, thermal expansion on a closed plumbing system, or high household water pressure. Never cap, plug, or block a leaking T&P valve — that's what it's there to prevent. Lower the thermostat and have a plumber replace the valve and find the cause.

No. A tankless unit has no storage tank to corrode, so water at its base usually comes from a loose fitting, the pressure-relief valve, or the condensate drain — those are repairs. Less often it's a cracked internal heat exchanger, which normally means replacing the unit. Because you can't tell which from the outside, shut off the water and gas or power and have a pro diagnose it before running it again.

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.

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.

Installed replacement in 2026 typically runs about $700–$1,800 for an electric tank, $1,000–$3,000 for a gas tank, and $1,200–$4,500 for a tankless unit — electric at the low end of that range, gas at the high end — with labor making up roughly 30–50% of the total. A straightforward same-location swap is at the low end; relocating the unit, upsizing gas or venting, or bringing old connections up to code pushes it higher. These are typical ranges, not quotes — get two or three local estimates.

A like-for-like tank swap is usually about 2–4 hours once the plumber is on site: pulling and draining the old unit, setting the new one, and remaking the connections. It runs longer if the old connections, venting, or drain pan have to be brought up to code, if the heater moves to a different spot, or if you switch to tankless, which adds gas or electrical work. Where a permit is required, the inspection is normally a separate short visit a day or two afterwards. Labor is roughly 30–50% of the installed cost.

Usually yes. Most US cities and counties require a permit and an inspection for a water heater replacement, because the job touches plumbing, gas or electrical connections, venting, and the T&P safety valve. The rules vary a lot: some states let a homeowner pull an owner-builder permit on their own home, while some cities require a licensed plumber even for a straight swap. A plumber normally pulls the permit as part of the job — it's one reason an installed replacement costs more than the price of the unit on the shelf. Check your local building department for what applies where you live.

It depends on your policy and on how the leak happened, so check with your insurer rather than assume. The general pattern in standard US homeowner policies is that sudden, accidental water damage — a tank that lets go and floods a room — is usually covered for the damage to floors, walls, and belongings, while the water heater itself is typically excluded, and a slow leak that has been seeping for weeks or a failure blamed on age and wear is commonly denied. Photograph the damage and the unit before anything is removed. If the tank is still inside its 6–12-year manufacturer warranty, ask about that separately — it may cover a replacement tank even though it won't cover the labor. This is general information, not insurance advice.

A licensed plumber. Water heaters are plumbing work in nearly every jurisdiction, and a plumber can both diagnose the leak and replace the unit. Two exceptions: if you smell gas, leave the house first and call your gas company or 911 from outside, and if the heater's breaker or wiring is involved, an electrician handles the panel side. If the tank is still under its manufacturer warranty, call the manufacturer or the installing plumber before you buy anything — a warranty tank may cost nothing even when the labor still does.