What should I do first when a water heater leaks?
A small puddle under a gas heater after heavy hot water use may be condensation (see below). If water keeps coming or spreading, do this in order:
- If you smell gas (a rotten egg or sulfur smell), leave first. Get everyone out. Do not relight the heater or any other appliance, and do not touch a light switch or use a phone anywhere inside the house. Call 911 or your gas company from outside; if that is Enbridge Gas Ohio, its 24/7 emergency line is 1-877-542-2630.
- Keep away from hot water and anything electrical. A water heater can make water hot enough to cause severe burns instantly, and Ready.gov says not to touch electrical equipment that is wet or while you are standing in water.
- Turn off the heat source, but only from a dry spot. On a gas heater, follow the label's shut down steps, usually turning the gas control's knob or switch to OFF, by hand, never with tools. A heater with a power cord (a power vent model, for example) is electrical equipment too: A.O. Smith's emergency shut down steps end with unplugging it, so do not touch a wet control, cord or outlet, and unplug it only from a dry spot. On an electric heater, switch off its breaker if you can reach the panel without standing in water. If you cannot, stay out of the water and call for help.
- Close the cold water valve on the pipe feeding the heater, usually at the top. If it will not turn or sits in the wet area, close the main shutoff where the water line enters the house.
- If the relief valve pipe pours very hot water, the tank may be overheating: turn the gas supply valve off (on an electric heater, the breaker) and call. The relief valve lets water out when tank temperature or pressure gets too high, so never cap or plug its pipe.
- Leave draining to the technician. A closed cold water valve stops new water, but a leaking tank can still let out what it holds, so move stored things off the floor. The manuals have you run the hot water until it is cool first, to avoid scalding, and warn that sediment can clog the drain valve.
- Note the model and serial number from the data plate on the tank.
If water reached the gas control, insulation or wiring, do not relight the heater: A.O. Smith says to have it inspected, and a heater whose gas control was submerged must be replaced. American Water Heater says the same of an electric heater's thermostats and insulation. An active leak you cannot stop is a call for our 24/7 emergency line: (216) 888-4822.
Why is my water heater leaking from the bottom?
Either the tank has corroded through, or water from somewhere else collects at the base: a pipe connection on top, the relief valve or its pipe, the drain valve near the bottom, or condensation. A 2023 gas manual on A.O. Smith's site notes that many suspected leaks are not the tank.
Tanks fail from the inside. The glass lined tank is guarded by an anode rod, a sacrificial metal rod that corrodes so the tank does not. Once the anode is used up, the tank starts to corrode and eventually leaks. Several things speed that up:
- Sediment left in the tank can deteriorate the tank and drain valve and cause leaks.
- High water pressure can cause premature leaks. A.O. Smith recommends a working pressure no higher than 50 to 60 psi (pounds per square inch).
- Thermal expansion. Water expands as it heats. When a check valve or backflow preventer stops it flowing back into the public supply, pressure rises, which can cause premature tank failure.
- A water softener makes the anode rod deplete faster.
- Plumbing leaks left alone can cause early tank failure from corrosion.
Is it the tank, or something that can be fixed?
Where water shows up first usually tells you. Fittings, valves and pipes can usually be fixed; a leaking tank cannot.
Dry everything off, then watch. A seep from under the outer jacket can still be a top fitting leaking where it enters the tank, because that water runs down inside the jacket. The 2023 gas manual checks this by pushing a cotton swab between the jacket opening and each fitting. If the swabs come out dry and it is not condensation, the tank is what is left.
| Where you see water | Likely cause | Fixable? |
|---|---|---|
| Beads on the pipes above the heater | Condensation in humid weather, or a leaking connection | Yes |
| Drips from the drain valve near the bottom | Valve not fully closed, or leaking at its threads | Usually |
| End of the relief valve pipe | High pressure or thermal expansion; lots of very hot water can mean overheating | Usually; never cap the pipe |
| Around the relief valve or anode fitting on top | Threads leaking where the fitting enters the tank | Usually, by resealing the fitting |
| Puddle and a sizzle under a gas heater after heavy hot water use | Condensation from the burner on a cold tank | Normal, it clears as the tank warms |
| Steady seep from under the jacket, swab test on the top fittings dry, tank fully hot | Corroded tank | No |
Most rows come from that manual's leakage checkpoints, which say not to replace a heater until every possible source has been checked.
Condensation or a real leak?
Burning gas makes water vapor, which condenses on a cold tank and drips onto the burner. The 2023 gas manual says this should stop once the tank warms up, in about 1 to 2 hours, and is heaviest in winter and early spring, when incoming water is coldest. After a run of showers on a January morning in Northeast Ohio, a puddle under a gas heater is not automatically a dead tank. If water keeps appearing once the tank is fully hot, look elsewhere. This check needs the burner running; if you shut the heater off because water was spreading, leave it off for the technician.
Can a leaking water heater be repaired, or does it need replacing?
Leaks from valves, fittings and pipes can usually be repaired. A leak through the tank itself means replacing the water heater.
- Repair: a drain valve left open or leaking at its threads, a loose connection, a relief valve that will not reseat (a qualified person replaces it), or one dripping from high house pressure or a missing expansion tank (it absorbs the pressure rise), where the fix is lowering the pressure or adding the tank, not replacing the heater.
- Replace: a leaking tank, or a heater whose gas control or thermostats have been under water. None of the three manufacturer manuals cited below offers a tank repair.
If the leak is fixable but the heater is old, weigh the repair against its age.
How long do water heaters last?
Tank water heaters are generally considered to last 10 to 15 years, according to a U.S. Department of Energy guide, and ENERGY STAR puts a gas tankless water heater's life expectancy at 20 years.
Those are national figures. The 2023 gas manual says water heater life depends on water quality, water pressure and where the heater is installed.
A.O. Smith recommends draining and flushing the tank and inspecting the anode rod after the first six months, then at least once a year, or more often if your water is hard. We install tank and tankless water heaters with isolation valves so they can be flushed.
What are the signs a water heater is going bad?
Water at the base that is not condensation or a fitting is the clearest sign. Others, especially on an older tank:
- Less hot water than you are used to. A.O. Smith lists sediment or lime on the tank bottom among the causes, and heavy deposits can damage the heater. Its other causes include an undersized heater, a melted dip tube (the plastic inlet tube inside the tank) and a leak on the hot side of the plumbing.
- Rumbling or popping. American Water Heater's electric manual says some noise is normal expansion and contraction, but sediment also makes noise and may cause premature tank failure.
- A relief valve that keeps dripping. That usually means water pressure is too high or the house needs an expansion tank, and high pressure itself can cause premature leaks.
What should a proper replacement include?
The right size for the household, plus the parts that protect the new tank and the house. A.O. Smith calls a new water heater the perfect time to bring the plumbing up to current code.
| Part or check | Why it matters |
|---|---|
| Isolation valves | Let the heater be shut off and flushed; we fit them every time. |
| Thermal expansion tank | Absorbs the pressure rise as water heats in a closed system. We fit one where code calls for it; A.O. Smith says codes require one in almost all homes. |
| Drain pan piped to a drain | Catches condensation or a leak and carries it to a drain. A.O. Smith recommends one, and we fit one when the location warrants it. |
| New relief valve, discharge pipe checked | Prevents excessive temperature and pressure. Do not reuse the old valve; in cold climates the pipe should end at an indoor drain, because outside drains can freeze. |
| Venting check (gas) | Good venting carries the exhaust out of the house. |
The cost mostly turns on tank or tankless, gas or electric, venting changes, access, and which parts above are missing today. An on site look gives a real number.
When to call Raber HVAC
- Water is still spreading, or you cannot shut it off: call the 24/7 emergency line, (216) 888-4822.
- The leak has stopped and the heater is off: call (216) 888-4822 any day from 8:00 AM to 10:00 PM, or book online: pick a day and an arrival window, and the office calls to confirm.
- You smell gas (rotten eggs or sulfur): get everyone out and call 911 or your gas company from outside.
Sources
- A.O. Smith, Residential Gas Water Heater Use & Care Guide (2025)
- Residential Gas Water Heaters Manual, power direct vent (2023, no brand printed; on A.O. Smith's hotwater.com)
- American Water Heater Company, Residential Electric Water Heater Use & Care Guide (2011)
- U.S. Department of Energy, Measure Guideline: Transitioning to a Tankless Water Heater (2012)
- ENERGY STAR, Save More with Gas Tankless Water Heaters
- Enbridge Gas Ohio, Safety
- Ready.gov, Floods