Do this now
- If you smell gas, leave the house and call the gas utility or 911 from outside.
- Turn off the power at the breaker for an electric heater, or turn the gas control to “off” for a gas heater.
- Close the cold-water shutoff valve on the pipe above the heater.
- If the tank is leaking, attach a hose to the drain valve and drain it to a floor drain or outdoors — the water may be very hot.
- Mop up and move stored items, then call a plumber.
What usually causes it
- A tank that has corroded through from the inside
- A leaking drain valve or loose supply connection
- A temperature-and-pressure relief valve that is discharging
- Condensation on a cold tank, which is not a leak
What a professional will do
A plumber finds where the water is coming from. Valves, connections and elements can be replaced; a tank that leaks from its body must be replaced. Installation involves gas or electrical connections, venting and a properly piped relief valve, and commonly requires a permit.
How to prevent it
- Check around the base of the heater a few times a year
- Flush sediment from the tank as the manufacturer recommends
- Have the anode rod checked on tanks more than a few years old
- Note the installation date; plan replacement as a tank approaches the end of its expected life
Rules and paperwork in Pennsylvania
- Pennsylvania’s Home Improvement Consumer Protection Act requires most contractors who perform home improvements to register with the Attorney General’s office and to give you a written contract for any job over $500. The registration number belongs on the estimate and the contract — ask for it.
- Building permits in Pennsylvania are issued under the Uniform Construction Code by each municipality or the inspection agency it appoints, so the local building or codes office decides what needs a permit and an inspection.
- Pennsylvania does not issue a statewide license for this trade. Some municipalities register or license it locally, which is one reason to confirm requirements with your own municipality.
Sources: Pennsylvania Office of Attorney General — Home Improvement Consumer Protection Act; Pennsylvania Department of Labor & Industry — Uniform Construction Code; Pennsylvania Department of Labor & Industry. Rules change — confirm current requirements with the agency and with your municipality.
Frequently asked questions
The relief valve is dripping. Is that a leak?
It is the valve doing its job or failing. It can mean excessive pressure or temperature, so do not cap it — have a plumber check it.
Can a leaking tank be patched?
No. Once the tank wall has corroded through, the heater has to be replaced.
Tank or tankless?
Tank heaters cost less to install and are simple to replace like for like. Tankless units save space and heat on demand but may need larger gas piping, new venting or electrical work.
Go deeper
Our full plumbing guide covers how the work is done, what affects the price, and what to ask before you hire, and there is more on water heater repair & installation.
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This guide is general information, not a substitute for a professional assessing your home. If you are unsure whether something is safe, treat it as if it is not.