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No hot water: safe checks for gas and electric water heaters

A cold shower usually traces back to a tripped breaker, a reset button or a pilot that went out. Here's what a homeowner can safely check, and where to stop.

Updated · 7 min read

  • DifficultyModerate
  • Time15–45 minutes
  • If you need helpPlumber

Nothing wakes you up faster than a cold shower. When the hot water disappears, the water heater has usually stopped heating for one of a few reasons: the power was cut, a safety switch tripped, or, on a gas model, the pilot or burner went out.

Some of these you can check yourself in 15 to 45 minutes. Others are firmly a job for a plumber. Water heaters hold a large tank of very hot water under pressure and use either high-voltage electricity or gas, so this guide sticks to the checks the manufacturers say are safe for homeowners.

First, figure out which type you have. A gas water heater has a gas pipe running to a control knob near the bottom and a metal vent pipe on top. An electric one has a thick electrical cable going into the top and one or two small metal access panels on the side.

What you'll need

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Electric: check the breaker

A.O. Smith calls a tripped breaker a very common reason an electric water heater stops working.

  1. Find the breaker. It's usually a double-wide breaker labeled "water heater." Our guide to reading your breaker panel can help.
  2. Reset it. Push it firmly to off, then on. See how to reset a tripped breaker.
  3. Wait. A full tank takes time to heat. Check again in an hour or so.
  4. If it trips again, stop. Leave the breaker off and call a plumber or electrician.

Electric: press the high-limit reset

Electric water heaters have a safety switch that shuts off power if the water gets too hot. A.O. Smith says it's usually a red button labeled ECO (energy cut off), behind the upper access panel above the upper thermostat.

  1. Turn off the breaker. Confirm power is off with a non-contact voltage tester at the access panel.
  2. Read the label. Your heater's label or manual explains its reset. Follow it if it differs from these steps.
  3. Remove the upper access panel. Move any insulation aside carefully. Many models have a plastic safety cover. Don't touch any wires or terminals.
  4. Press the red button firmly. A.O. Smith says to press until you hear a click. If it doesn't click, it wasn't tripped.
  5. Put everything back. Replace the insulation, the cover and the panel before turning the breaker back on.

If the reset trips again, don't keep pressing it. A.O. Smith says repeated trips point to serious problems like shorted elements or a faulty thermostat.

One more warning: never turn power on to an electric water heater with an empty tank. A.O. Smith warns that the heating element can burn out if the tank isn't full.

Gas: check the gas supply and pilot

On a gas water heater, the burner may not light if the gas valve is off or the pilot went out.

  1. Check for a gas smell. If you smell gas, stop here and leave.
  2. Check the gas valve. Look for the shutoff valve on the gas pipe leading to the heater. It's open when the handle lines up with the pipe.
  3. Check the control. Make sure the knob on the gas control isn't set to Off or Vacation.
  4. Look for the pilot or status light. Older models have a small window to see the pilot flame. Many newer models have a status light that blinks a code. Your manual or the label explains the codes.
  5. Relight only by the label. A.O. Smith directs you to light the pilot using the lighting instructions and safety information on the water heater itself. If you can't find or read the label, or you're not comfortable, call a plumber.

If the pilot won't light or won't stay lit, stop. Don't take apart the gas control, the burner or any gas fittings. Those parts are for licensed professionals.

Check the temperature setting

Sometimes the water is just lukewarm because someone turned the dial down. A.O. Smith suggests 120°F as a good balance of heating speed, energy cost and safety. Higher settings increase the risk of scalding, especially for children and older adults.

A word about the T&P valve

Every tank water heater has a temperature and pressure (T&P) relief valve, usually a lever on the top or side with a pipe running down. It opens to release water if the tank gets too hot or the pressure too high. It's a critical safety device.

  • Never cap, plug or remove the T&P valve or its pipe.
  • If it drips or sprays, call a plumber. A.O. Smith notes that a dripping valve often points to high water pressure or thermal expansion, which should be fixed first.
  • Inspect it only as the label on the valve instructs. A.O. Smith warns that scalding water can shoot out of it.

Flush out sediment

Minerals settle at the bottom of the tank over time. A.O. Smith says this buildup slows heating and causes rumbling or popping sounds, and suggests draining a few gallons once a year, more often with hard water. If you're comfortable, here's the basic process from their maintenance guide:

  1. Turn the heater off. Turn off the breaker on electric models. Set a gas model to Pilot or Off as the label directs.
  2. Let the water cool. Waiting a few hours lowers the scald risk.
  3. Close the cold water supply valve at the top of the heater.
  4. Attach a hose to the drain valve at the bottom and run it to a floor drain or outside.
  5. Open a hot water faucet somewhere in the house so air can get in, then open the drain valve and let 2 to 3 gallons run out.
  6. Close the drain, reopen the cold supply and let the hot faucet run until water flows steadily, then turn the heater back on.

If the drain valve won't close or leaks, call a plumber.

When to call a pro

Call a licensed plumber if:

  • You smell gas, see scorch marks or soot, or the pilot won't stay lit.
  • The breaker or the ECO reset trips again.
  • Water is leaking from the tank, or the T&P valve drips or sprays.
  • A gas model's status light blinks an error code your manual says needs service.
  • Your heater is older and you're deciding whether to repair or replace it. Codes and permits for new water heaters vary by city and county, and a licensed plumber will know your local rules.
  • You rent. Water heater repairs are usually your landlord's job.

Read how to choose a plumber, or take our fix it or call a pro quiz.

Keep it from happening again

  • Drain a few gallons once a year to clear sediment, more often with hard water.
  • Keep the area around the water heater clear so you can reach the valves and, on gas models, so air screens aren't blocked.
  • Keep the temperature around 120°F.
  • Know where your water shutoff is. See how to find your water shutoff.
  • Install a carbon monoxide alarm if you have a gas water heater.

Common questions

Where is the reset button on an electric water heater?

On many electric models, A.O. Smith says the red reset button (often labeled ECO, for energy cut off) sits behind the upper access panel, above the upper thermostat. Turn off the breaker before you remove the panel, and follow the label on your heater.

What does it mean if the water heater reset button keeps tripping?

The button trips when the water gets too hot. A.O. Smith says repeated trips point to serious problems such as shorted elements or a faulty thermostat. Stop resetting it and call a pro.

How do I relight my water heater pilot?

Only follow the lighting instructions printed on the label on your water heater. If there's no label, you can't read it, or you smell gas, don't try. Call a plumber or your gas company.

What temperature should my water heater be set to?

A.O. Smith suggests 120°F as a good balance of heating speed, energy cost and safety. Higher settings raise the risk of scalding.

Sources

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