Water Heater: No Hot Water (Gas & Electric)
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Quick answer: A. O. Smith says the first thing to check is the circuit breaker on an electric heater, or that the pilot is lit and the gas valve is open on a gas heater. Electric: next press the red reset button (Energy Cut Off) behind the upper access panel with power off. Gas: relight the pilot per the label. If the reset keeps tripping or the pilot won’t stay lit, call a professional.
⚠ Safety first (A. O. Smith): Electric: turn off power at the circuit breaker before touching anything; components can be live even when the unit isn’t heating. Gas: if you smell rotten eggs or suspect a leak, turn off the gas supply valve immediately and call a professional; don’t keep troubleshooting. Let the heater cool before removing panels, and keep clear of the pressure relief valve. Rheem: do not use a water heater if any part has been under water; call a qualified service agency.
Electric: test order
- Check the circuit breaker / fuseFREE · 5 min
A. O. Smith calls a tripped breaker a very common cause. Reset it, and have it checked for shorts, loose wires or grounded elements. - Press the red reset buttonFREE · 10 min
Turn off power at the breaker, remove the upper thermostat access panel, and press the red reset button (Energy Cut Off) until it clicks; then restore power and test (A. O. Smith). Rheem: the cause of the high-temperature condition must be investigated by a qualified technician. If it trips repeatedly, A. O. Smith says to call a pro (shorted elements or faulty thermostats). - Heating elementsPRO / PART
A. O. Smith lists faulty heating elements; fix is to test and replace. A. O. Smith recommends a professional replace thermostats and elements. - ThermostatPRO / PART
A. O. Smith: thermostat issues can trip the high-limit switch, often due to a grounded element or faulty lower thermostat.
Gas: test order
- Check the gas valveFREE · 2 min
Make sure the gas valve is open; gas supply problems prevent burner ignition and can put the pilot out (A. O. Smith). - Is the pilot lit?FREE · 2 min
Look for a visible flame; if there is one, the pilot is still lit (A. O. Smith). - Relight the pilotFREE · 15 min
Follow the lighting label on your heater first; it supersedes general guides. A. O. Smith’s steps: turn the gas control off and wait at least 10 minutes for gas to dissipate, set the knob to “Pilot” and push it in, light it (ignitor button or lighter per your model), then release slowly and make sure it stays lit before turning to On. Do not continue if you smell gas. - Pilot won’t stay litINSPECT / PRO
A. O. Smith lists gas pressure changes, a faulty thermocouple/thermopile, drafts, lack of combustion air, kinked or clogged tubes, and control valve failure. Lack of air can release carbon monoxide; get a tech in before relighting. A failed control valve or ignition system needs a service visit. - Air screens and burnerINSPECT
A. O. Smith: blocked air screens/filters restrict combustion air; a clogged burner assembly should be cleaned with gas and water off, or replaced by a professional.
Parts to check
| Part | Part number | |
|---|---|---|
| Heating element (electric) | Look up by your model number | Check price [PLACEHOLDER – no affiliate link] |
| Thermostat (electric) | Look up by your model number | Check price [PLACEHOLDER – no affiliate link] |
| Thermocouple / thermopile (gas) | Look up by your model number | Check price [PLACEHOLDER – no affiliate link] |
We only list part numbers confirmed by a cited source. Parts vary by model, so always look up by the model number on the heater’s rating label before ordering.
💡 Just had a big demand? A. O. Smith gives recovery times of 30–40 minutes for gas tanks and 60–90 minutes for electric tanks.
Watch it done
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