No Hot Water? Troubleshooting Guide
Losing hot water suddenly is almost always one of a few simple things. Diagnose by heater type — gas or electric — and work through these before calling for service.
Gas Heater: Check the Pilot / Burner
If you have a standing pilot, look through the sight glass at the bottom — if the flame is out, follow the relight instructions printed on the tank. If it will not stay lit, the thermocouple is likely failing. Newer gas heaters have an electronic igniter; a blinking status light on the gas valve tells you the fault code (check the label).
Electric Heater: Reset Button First
Electric heaters have a red reset button on the upper thermostat behind the access panel. A tripped high-limit reset is the most common cause of sudden no-hot-water. Turn off the breaker, remove the upper panel, press the red button, and restore power. If it trips again, a thermostat or element has failed.
Electric Heater: Check the Breaker and Elements
Confirm the double-pole breaker is not tripped. If power is good and the reset is set, one of the two heating elements may have burned out — a common cause of "lukewarm" or "runs out fast." Elements are inexpensive and testable with a multimeter.
Lukewarm or Runs Out Fast
Hot water that does not last usually means the lower element failed (electric), the dip tube cracked (mixing cold into hot), or heavy sediment has shrunk the tank's usable volume. Flushing the tank and testing the lower element are the next steps.
Parts & Tools
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FAQ
On electric heaters it is the red button on the upper thermostat, behind the top access panel and under the insulation. Press it after cutting power at the breaker.
Usually a failed lower heating element (electric), a broken dip tube, or sediment buildup reducing tank capacity. Test the lower element and flush the tank.
Always unplug an appliance and shut off its water supply before servicing. This guide is informational and not a substitute for a qualified technician.