Short answer
If you have no hot water and you smell gas, leave the house and call from outside. No gas smell? On a gas heater, look through the little window at the bottom: if the pilot is out, relight it following the label on the tank. On an electric heater, reset its breaker once. Then check the temperature dial is not on Vacation or Low, and give it about an hour to reheat.
Safety first
Gas smell? Get everyone out, do not flip switches or use your phone inside, and call 911 or your gas company from outside. Never relight a pilot if you smell gas. On an electric heater, stand on a dry floor and reset its breaker only once: if it trips again, leave it off.
What to check when you have no hot water
1No hot water? Check for gas first
If you smell gas near the heater, do not touch anything. Get everyone out and call 911 or the gas company from outside.
Read all the steps
- No hot water? Check for gas first. If you smell gas near the heater, do not touch anything. Get everyone out and call 911 or the gas company from outside.
- Gas heater: look for the pilot flame. Look through the small window near the bottom of the tank. No small flame means the pilot is out. Relight it following the label on the tank.
- Electric heater: reset the breaker once. Find the breaker marked water heater or WH. Push it fully to OFF, then back to ON. If it trips again, leave it off and call.
- Set the dial near 120°F. It may have been bumped to Vacation or Low. Turn the dial on the gas control back to about 120°F. On electric heaters it sits behind a panel: call a pro.
- Give it about an hour to reheat. A full tank takes time: often 30 to 60 minutes on gas, longer on electric. Still cold after that? Call a plumber.
- Still not fixed? Call a plumber Especially if: still no hot water after an hour, or the pilot will not stay lit.
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If only one faucet has no hot water
When one faucet runs cold but the others are hot, the heater is fine: the problem is that faucet, often a stuck cartridge or a clogged aerator. Lukewarm water everywhere, or hot water runs out after a few minutes? Then a part inside the heater may be failing.
Why it happens
On gas heaters the usual causes are a pilot that went out, a worn thermocouple or a problem with the gas supply. On electric heaters it is often a tripped breaker, a burned-out heating element or a failed temperature control. If the tank is also wet at the base, see what to do about a leaking water heater.
What not to do
- Do not relight the pilot if you smell gas, and never use a match on a heater with a sealed burner door.
- Do not open the panels on an electric heater: the parts behind them carry high voltage.
- Do not keep resetting a breaker that trips. Twice means something is wrong.
- Do not turn the dial all the way up. Hotter settings scald faster, especially kids and older adults.
When to call a plumber
- Still no hot water after an hour, or the pilot will not stay lit.
- Any gas smell (call 911 or the gas company first, from outside).
- The breaker trips again after one reset.
- Water around the base of the tank, or rusty hot water.
Frequently asked questions
Why do I suddenly have no hot water?
On a gas heater, most often the pilot went out or the gas control was turned to Pilot or Off. On an electric heater, it is usually a tripped breaker or a burned-out heating element. Check those first, then call a plumber.
How do I know if my water heater is gas or electric?
A gas heater has a gas pipe going into a control box near the bottom and a metal vent pipe on top. An electric heater has a thick electrical cable going into the top and no vent pipe.
How long does it take to get hot water back?
Usually 30 to 60 minutes for a gas heater after it relights, and up to about two hours for an electric one. If it is still cold after that, call a plumber.
Why is there no hot water but the cold works fine?
Because the hot side depends on the heater. If every hot faucet is cold, check the heater. If only one faucet is cold, the problem is in that faucet.
Can I reset my water heater myself?
You can reset the breaker of an electric heater once from the panel. The reset button on the heater itself sits behind a panel with live wires, so leave that to a pro. Most gas heaters reset by relighting the pilot.
Is no hot water an emergency?
Not usually, unless you smell gas, see water leaking or someone at home needs hot water for health reasons. Use the "24/7 emergencies" filter to find plumbers who answer now.