Electric water heaters
Electric heaters have two heating elements, each with its own thermostat, plus a high-limit reset button behind the upper access panel.
- No hot water at all: check the breaker, then press the red reset button (power off first)
- Hot water runs out fast: the lower element has likely failed
- Water is lukewarm: a thermostat or upper element problem
Gas water heaters
Gas heaters use a pilot or electronic igniter. The control knob should be set to On, not Pilot or Vacation.
- Pilot won't stay lit: usually the thermocouple or flame sensor
- Pilot lit but no burner flame: gas valve or control problem
- Smell gas: leave the house and call the gas utility from outside
Hot water, but not enough
Sediment settling in the bottom of the tank takes up space and insulates the water from the burner. Rumbling and popping while heating is the sign. Flushing helps on younger tanks; on an old tank, heavy sediment is a sign it's near the end.
Repair or replace a heater that won't heat?
Parts like elements, thermostats and thermocouples are worth replacing on a heater under about eight years old. A heater over ten years old needing a major part, or any tank leaking from its body, is usually a replacement — see our guide on when to replace a water heater.
What a plumber checks on a cold water heater
On gas heaters: the pilot or igniter, thermocouple or flame sensor, gas valve and venting. On electric heaters: the breaker, the upper and lower heating elements and thermostats. The plumber tests each part and replaces the failed one, or recommends replacement if the tank is old or leaking.
Water Heater Not Heating? Troubleshooting: when to call a pro
- You smell gas
- The relief valve is discharging
- Water is leaking from the tank body
Water Heater Not Heating? Troubleshooting: common questions
Why do I have some hot water but it runs out quickly?
On an electric heater, a failed lower element is the usual cause. On any tank, heavy sediment can also reduce capacity.
Is it safe to relight a water heater pilot myself?
Yes, if you follow the instructions on the heater label and don't smell gas. If you smell gas, leave the house and call the gas utility from outside.
Why is my electric water heater not heating?
A tripped breaker, a tripped high-limit reset button, or a failed heating element or thermostat are the usual causes.
Why does my gas water heater pilot keep going out?
Most often a worn thermocouple or flame sensor. If you smell gas, leave and call the gas utility first.
Every home differs; editorial standards.