Repair guide
No hot water
Updated 30 Sep 2026 · AR Logic LLC · 2 sources
Rarely an emergency
If no tap in the house runs hot, the water heater has lost its heat source: on an electric heater, a tripped breaker or a tripped high-limit (ECO) switch; on a gas heater, a pilot or burner that has gone out or a closed gas valve. If only one tap is cold, the problem is that tap’s mixing valve, not the heater.
Is no hot water an emergency?
Rarely on its own. It is an emergency if you smell gas (leave and call the gas company or 911 from outside), if water is pooling around the tank, or if the relief valve on the side is spraying. No hot water in a rental is usually a same-day repair for the landlord.
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Managers: set it up for your buildings →What to check, in order
One tap or all of them?
One cold tap is a faucet or shower valve problem. All cold, including the kitchen, is the heater.
Electric: the breaker and the disconnect
Make sure the water heater’s breaker is on and any disconnect switch beside it is on; check the fuses if it has them [1].
Electric: the high-limit (ECO) reset
If the water was very hot and is now cold, the over-temperature switch may have tripped. With the power off, remove the access cover and press the red reset button on the thermostat; if it trips again, the thermostat or element is faulty — call a pro [1].
Gas: is the pilot or burner lit?
Look through the sight glass at the bottom. If the pilot is out, relight it by the instructions on the label on the tank — and only if you smell no gas. A pilot that keeps going out often points at the thermocouple or flame sensor.
Gas: the supply valve
The valve on the gas line to the heater should be open (handle in line with the pipe). If other gas appliances are also out, call the gas company.
Heavy use or a small tank
Hot water that runs out quickly after showers or laundry can simply be demand beyond the tank’s size [1]; sediment build-up also cuts capacity, which is why makers recommend flushing the tank [2].
Safety first
- If you smell gas, do not relight anything: leave and call from outside.
- Switch off the breaker before removing an electric heater’s access covers — both elements run on 240 volts.
- Water from a heater can scald; the relief valve discharges very hot water.
When to call a pro
Call a plumber if the reset trips again, the pilot will not stay lit, you smell gas, or water is on the floor.
What to photograph
For the Triage Profile, photograph the whole water heater with its label, and the sight glass or the thermostat cover if you can see it. One clear photo in good light is enough; the Triage Profile says what it is, how urgent it is (emergency, today, this week or whenever), and which trade to call.
Questions people ask
How long does a water heater take to recover?
It depends on the tank size and the heater; electric tanks generally reheat more slowly than gas ones. If the water never gets hot again, it is not recovery — work through the checks above.
Is it the heater or the shower valve?
If the kitchen tap runs hot and the shower does not, it is the shower valve.
Sources
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Snap a photo of it. The Triage Profile says what it is, how urgent it is, and who to call.