No hot water?

On a gas heater the usual suspects are a pilot that went out or a worn thermocouple. On an electric one it is a tripped breaker, the reset button, or a heating element. If the hot water runs out fast or is only lukewarm, sediment, an undersized tank or a dip tube is more likely.

Not sure which one it is? Snap your water heater and we’ll narrow it down.

Is there hot water, but water is pooling around the heater?

Where it leaks decides the fix. Water heater leaking

Likely causes

  1. Gas: pilot light out

    Most commonModerate DIY

    A gas heater with no hot water at all, and no flame visible in the pilot window. Relight it only by the instructions on the unit's label. A service call to relight it runs $50–150.

    Part: $50–150 (service call to relight the pilot)

  2. Gas: worn thermocouple

    Most commonCall a pro

    The pilot goes out again after relighting, which is the usual sign of a worn thermocouple.

    Part: $150 (installed)

  3. Electric: tripped breaker or reset button

    Most commonModerate DIY

    An electric heater with no hot water at all. The 240V breaker is tripped, or the red reset button on the upper thermostat has popped. If either trips again right after you reset it, something is failing.

  4. Electric: failed heating element or thermostat

    CommonCall a pro

    The breaker is on and the reset is pressed, but the water is cold or lukewarm, or the hot water runs out quickly because only one of the two elements still heats.

    Part: $200–300 (heating element); $150–200 (thermostat)

  5. Sediment buildup or an undersized tank

    CommonCall a pro

    There is hot water at first, then it runs out sooner than it used to. Rumbling or popping from the tank points to sediment. A tank that never kept up with the household is simply too small.

    Part: $200 (flush)

  6. Thermostat set too low

    CommonEasy DIY

    The water is warm but never hot. Someone may have turned the dial down, or it was knocked.

  7. Broken dip tube

    Less commonCall a pro

    Lukewarm water, because the cold water entering the tank mixes with the hot at the top instead of sinking to the bottom.

    Part: $25–175

  8. Gas: failed gas control valve or no gas supply

    Less commonCall a pro

    The pilot won't stay lit or the burner won't fire even after a fresh start, or other gas appliances are also off.

    Part: $350 (gas control valve)

Quick checks

If you smell gas (rotten eggs), leave the house immediately and call the gas company or 911 from outside. Don't touch any switches or lights. Relight a gas pilot only by the instructions on the unit's own label, and if it won't stay lit, call a pro. On an electric heater, switch the breaker off before opening any access panel. Hot water can scald, so keep the thermostat at the manufacturer's recommended setting.

  1. Look at the label on the tank to see whether it is gas or electric, and check the temperature setting on the thermostat dial. Keep it at the manufacturer's recommended setting.
  2. Electric: check that the 240V breaker in the panel hasn't tripped, and reset it once. If it trips again, leave it off and call a pro.
  3. Electric: switch the breaker off before you open any access panel. Then you can press the red reset button on the upper thermostat once.
  4. Gas: look through the pilot window to see whether the pilot flame is lit. Don't open anything.
  5. Gas: check that the gas valve on the supply line is in line with the pipe (open), and ask whether other gas appliances work.
  6. If the hot water runs out fast, note how long it lasts and whether the tank rumbles, and photograph the label for the size and rating.
Sharpen the read

Diagnose your water heater in seconds, for free

No account, no phone number. Fixology’s AI reads your photo and tells you what’s likely wrong, how worried to be, and whether it’s a DIY fix.

Snap one of these:

  • the model and rating label on the tank
  • the top of the tank with its pipes and valves
  • the pilot window or the access panel (don't open it)

Add a note or more photos next. Nobody calls you.

When to call a pro

A gas heater won't stay lit or you smell gas, an electric breaker or reset keeps tripping, an element or thermostat needs replacing, the water is still lukewarm after the thermostat check, or the tank is more than 10–15 years old. HomeAdvisor puts tank lifespan at about 10–15 years. For leaks, see water heater leaking. For lifespan and upkeep, see the water heater guide.

Typical cost: HomeAdvisor puts water heater repair at $228–1,017 (about $616 on average). Gas units run $150–500 and electric units $20–300. Relighting a pilot (a service call) is $50–150. Replacement runs $875–1,800.

Sources: HomeAdvisor: How much does a water heater repair cost? (updated June 17, 2026)

After a scan, Fixology can also help you find pros near you.

Related problems

  • Water heater leaking?

    Water heater

    Water around the heater: where it comes from decides whether it's a fixable fitting or valve, or a tank that has to be replaced.

  • Furnace won't heat?

    FurnaceFall

    The furnace runs but the house stays cold, which is usually a clogged filter, a thermostat setting, or an ignition fault.

  • Heat pump not heating?

    Heat pumpFall

    The heat pump runs but the house stays cold, which is usually thermostat settings, a clogged filter, or an iced-over outdoor unit.

  • Washer won't drain?

    Washer

    Water is left in the drum after the cycle, which is usually a clogged pump filter or a kinked drain hose.

Fixology helps you understand your home — it isn't a substitute for a licensed pro on serious gas, electrical, or structural work.