How a typical electric tank works
Most residential electric tanks have two heating elements, one high and one low, each controlled by its own thermostat behind a removable panel. The upper thermostat usually runs first, heating the top of the tank, then hands off to the lower element.
A high-limit switch, often combined with the upper thermostat, cuts power if the water gets dangerously hot. When it trips, the heater goes cold until someone finds out why and resets it.
Symptoms and usual causes
| Symptom | Usual cause |
|---|---|
| No hot water at all | Tripped breaker, tripped high-limit, or failed upper element or thermostat |
| Some hot water that runs out fast | Failed lower element |
| Water too hot | Thermostat stuck on or set too high; check before the high-limit trips |
| Breaker trips repeatedly | Shorted element or wiring fault |
| Lower element fails again and again | Sediment burying the element |
What you can check safely
- IfThe breaker is trippedReset it once. If it trips again, leave it off and call a professional.
- IfThe breaker is on but the tank is coldDo not open panels. A plumber can test whether the high-limit tripped and why.
- IfWater is scalding hotTurn off the breaker and have the thermostats checked. Do not just lower the dial and hope.
- IfWater is leaking from a panelTurn off the breaker and the cold supply. Water and electricity together need a professional immediately.
What a plumber typically does
- Power off and verify.Shut off the circuit and confirm it is dead before opening anything.
- Test elements and thermostats.Check each element and thermostat to find which has failed.
- Find the cause of any trip.A high-limit trip has a reason: a stuck thermostat, a shorted element, or wiring.
- Replace and refill correctly.When an element is changed, the tank is refilled completely before power is restored, so the new element is never energized dry.
Terms
- Element
- A metal rod that heats when current runs through it, screwed into the tank wall.
- Thermostat
- A switch that turns an element on and off to hold the set temperature.
- High-limit switch
- A safety cutoff that shuts off power if the water overheats. Also called an energy cutoff.
- Dry fire
- Energizing an element without water around it, which destroys it almost immediately.
Common questions
- Why does my lower element keep burning out?
- In hard-water areas, sediment can bury the lower element so it overheats. Flushing, and sometimes a different element type, can help. Ask the plumber.
- Is it safe to press the high-limit reset button?
- It sits behind a panel near live wiring, and resetting it without finding the cause can mask a problem. Leave it to a professional.
- Is an element replacement worth it on an old tank?
- If the tank is dry and sound, often yes. On an older, sediment-heavy tank, compare the repair with a replacement in writing.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.