Home Doctor

Plumbing guide

No hot water: what to check on a gas or electric water heater

By the Home Doctor team · Reviewed

Quick answer

When a tank water heater stops making hot water, start with the simple things: a pilot that's gone out on a gas heater, or a tripped breaker or popped reset button on an electric one. If that's not it, the usual culprits are the thermocouple on a gas heater, or a heating element or thermostat on an electric one, and each typically costs $125 to $400 to have a plumber replace. If you smell gas, don't relight anything: leave the house and call your gas utility from outside.

How urgent
Fix soon

Miserable, but not dangerous by itself. It becomes 'stop and call a pro now' if you smell gas, see scorching, or the relief valve is blowing hot water.

DIY or pro
DIY if handy

Relighting a pilot and resetting a breaker or reset button are DIY. Swapping an electric element or thermostat is a handy job if you can safely test a 240-volt circuit. Gas valve work is for a plumber.

Stop and call a pro now if

  • You smell gas or rotten eggs: don't relight the pilot or flip any switches. Leave the house and call your gas utility or 911 from outside.
  • A carbon monoxide alarm is sounding: get everyone outside and call 911 from outside.
  • The T&P relief valve is blowing hot water or steam: stay clear, shut off the power or gas, and call a plumber. The tank may be overheating.
  • Soot or scorch marks around the burner door of a gas heater, or a burning smell or melted wiring on an electric one: shut it off and call a pro.

Common causes and how to tell them apart

  1. 1. A problem at one fixture, not the heater

    How to tell
    Other taps run hot. Only one shower or faucet stays cold.
    What fixes it
    The cartridge or anti-scald valve in that fixture is clogged or worn. Replace the cartridge.

  2. 2. Pilot out or won't stay lit (gas)

    How to tell
    No flame through the sight window at the bottom of the tank. On newer heaters, a status light may blink an error code.
    What fixes it
    Relight it by following the label on the tank. If it goes out when you let go of the knob, the thermocouple (the sensor that tells the gas valve the pilot is lit) is the usual suspect.

  3. 3. Gas supply or gas control valve (gas)

    How to tell
    The pilot is lit but the main burner never comes on, or none of your gas appliances work. Power-vent heaters, the ones with a fan on top, also stop if they lose electricity.
    What fixes it
    Check the temperature dial isn't on Vacation or Low, the gas valve on the supply pipe is open, and a power-vent unit is plugged in. A failed gas control valve is a plumber's job.

  4. 4. Tripped breaker or high-limit reset (electric)

    How to tell
    No hot water at all. The heater's breaker is tripped, or the red reset button behind the upper access panel has popped.
    What fixes it
    Reset the breaker once. With the breaker off, press the reset button. If it trips again, an element or thermostat is likely failing.

  5. 5. Failed heating element (electric)

    How to tell
    Lukewarm water, or hot water runs out much faster than it used to. That's usually the lower element. A failed upper element usually means no hot water at all.
    What fixes it
    With the power off, test the elements with a multimeter. Elements are cheap, but replacing one means partly draining the tank.

  6. 6. Failed thermostat (electric)

    How to tell
    The elements test good but the water stays cold, or the water gets scalding hot and the reset button keeps tripping.
    What fixes it
    Replace the thermostat with a matching one.

Not sure which one you have?

Snap a photo. Home Doctor narrows it down, tells you how urgent it is, and prices the fix.

Diagnose it from a photo

First diagnosis free. No account needed.

What you can safely try first

  1. 1Run hot water at a few taps to see whether it's the whole house or one fixture.
  2. 2Gas: look through the sight window for a flame. If the pilot is out and you don't smell gas, relight it by following the label on the tank. Check the dial isn't on Vacation.
  3. 3Electric: check the heater's breaker and reset it once if it's tripped.
  4. 4Electric: with the breaker off, remove the upper access panel, fold back the insulation and press the red reset button. Put it all back before turning the power on.
  5. 5Give it time. A gas tank takes about an hour to heat back up, an electric one two hours or more.

When to call a pro

  • The pilot won't light or won't stay lit.
  • The burner won't come on with the pilot lit.
  • The breaker or reset button trips again.
  • Any gas smell, soot, scorching, or water around the base of the tank.

What it costs

Typical costs to fix: no hot water
JobDIY partsPro, installed
Plumber diagnostic visit—$100–$300
Replace thermocouple (gas)$10–$30$125–$300
Replace heating element (electric)$15–$40$175–$400
Replace thermostat (electric)$20–$50$150–$350
Replace gas control valveNot recommended$250–$750
Replace a 40–50 gal tank water heaterNot recommended$1,200–$3,500

Ballpark US ranges as of September 27, 2026. Your region, access and the specifics of your home can move these a lot. Get two or three quotes for anything over a few hundred dollars.

What to tell the pro

My [gas / electric] tank water heater, about [age] years old, isn't making hot water [at any tap / at one fixture]. [The pilot won't stay lit / The pilot is lit but the burner won't come on / The breaker or reset button keeps tripping]. I've [relit the pilot / reset the breaker / pressed the reset button] and it [worked for a while / didn't help]. I don't smell gas and there's no water around the tank. Is it worth repairing at this age, and can you give me the price before you start?

Questions people ask

Why is there no hot water when the pilot light is on?

The pilot is lit but the main burner isn't firing. Check that the temperature dial isn't set to Vacation or Low. If it's set right and the burner still won't come on, the burner may be clogged or the gas control valve may have failed. Both are jobs for a plumber.

How do I reset an electric water heater?

Turn off its breaker first. Remove the upper access panel, fold back the insulation and any plastic guard, and press the red button on the thermostat, often labeled Reset or ECO. Put it all back, turn the breaker on and wait an hour or two. If it trips again, don't keep resetting it: an element or thermostat needs testing.

How long does it take to get hot water back?

After a relight or reset, a gas tank usually has hot water again in about an hour. An electric tank heating from cold can take two hours or more.

Should I repair or replace my water heater?

A thermocouple, element or thermostat is usually worth replacing. If the tank is 10 or more years old, is leaking, or needs a new gas valve, replacing it often makes more sense. Tank heaters typically last 8 to 12 years.

Get an answer for your house

Every house is different. A photo gets you the likely cause, how urgent it is, and a fair price, in about 30 seconds.

Diagnose it from a photo

First diagnosis free. No account needed.

General guidance, not a substitute for a licensed professional who can see the problem in person. If you smell gas, see sparks or smoke, or anyone is hurt, leave the area and call 911.