The tank itself is leaking. That is a replacement, not a repair.
A corroded tank does not reseal. It will keep leaking and can let go all at once, and 40 to 50 gallons on a floor is a restoration job.
What is probably happening
- Water at the bottom of the tank, or rust streaks down the side, means the inner tank has rusted through.
- A. O. Smith's own guidance: if the tank itself is leaking, the whole water heater usually needs to be replaced.
- Storage tank heaters last 10 to 15 years. Check the serial plate for the year.
Do this in the next five minutes
- Close the cold inlet valve on top of the heater (turn clockwise, or a quarter turn on a lever).
- Shut off the heater: gas control knob to Off, or the electric breaker off.
- Put a bucket or towels under the drip and move anything stored nearby.
- If you have a hose, attach it to the drain tap at the bottom and run it to a floor drain or outside, then open the tap and a hot faucet upstairs to let the tank drain.
- Photograph the serial plate and the leak for the plumber and the insurer.
Do not
- Do not run the heater with the tank empty or half empty. An electric element burns out dry in minutes.
- Do not accept a tank patch or sealant. There is no repair for a rusted tank.
- Do not let anyone skip the permit. Water heater replacement needs one in most jurisdictions and it is what checks the venting and the relief valve.
Who to call
A licensed plumber
Water heater replacement is plumbing work and, for gas units, gas work. An HVAC company may do it too, but the licence to check is plumbing.
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What it should cost
$882 to $1,826, averaging $1,347
Tank water heater replacement, installed, national range. Tankless runs $1,400 to $3,900
Source: Angi, water heater replacement cost, updated July 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the plumbing page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- Is the price for the same size and fuel as the old one, and does it include haul away, the permit and a new expansion tank if code requires one?
- Who pulls the permit and meets the inspector?
- What is the tank warranty in years, and what is your labor warranty on top?
- If I want a tankless, what does my gas line and venting need, and is that in the quote?
End the call if
- A quote with no permit. This is the inspection that catches a bad flue or a missing relief valve drain.
- Pressure to go tankless tonight. A tankless is a planned job, not an emergency swap.
- A price far under the range with no brand or model named.