Symptoms
- Some hot water available but it runs out faster than before
- No error indicator, since most tanks don't display one
- Breaker for the unit hasn't tripped
- Problem may have developed gradually or suddenly
Likely causes
- CommonLower element failed while upper element still worksThis typically still gives some hot water from the top portion of the tank, but much less total volume.
- PossibleUpper element failed while lower worksNon-simultaneous operation thermostats mean if the upper element fails, the lower may never get power until the upper is fixed, depending on wiring type.
- PossibleFailed thermostat for one element rather than the element itselfA thermostat controlling one element can fail and prevent that element from ever engaging.
What to do
- Turn off power to the water heater at the breaker before removing any access panels.
- Remove the panels, insulation, and plastic guards to access both elements and thermostats.
- Use a multimeter to test each element for continuity (resistance in the expected range, not open or shorted).
- Test each thermostat's continuity and switching behavior per the manufacturer's diagram if the elements themselves test fine.
- Replace whichever component tests bad, matching wattage and voltage specifications exactly.
- Refill the tank fully and confirm no air is trapped before restoring power, since running an element dry destroys it instantly.
Tools and parts
- Multimeter
- Element wrench
- Screwdriver
Water heater heating elementSearch: “electric water heater heating element replacement”
Water heater thermostatSearch: “electric water heater thermostat replacement”
When to call a pro
If you're not comfortable testing electrical components with a multimeter, a licensed electrician or appliance technician can diagnose and replace the faulty part.
Safety
Use caution
Confirm power is off with a voltage tester before touching any internal wiring, and never restore power until the tank is completely full of water.