Water Heater Heating Elements

How the two elements share the work

Most residential electric tanks have two elements, each with its own thermostat. They don't run at the same time. Bradford White's service manual describes the standard setup: the upper element heats first, and only when the upper thermostat is satisfied does power switch over to the lower thermostat and the lower element.

That sequence explains most of the symptoms people see:

• No hot water at all. The upper element or upper thermostat has usually failed, because the lower element never gets its turn.
• Hot water that runs out fast. The top of the tank heats, but the lower element is dead. HomeGuide lists this exact symptom as a sign of a faulty lower element.
• Lukewarm water. HomeGuide links lukewarm water to a bad upper element.

The lower element works the hardest in most homes. Cold water comes in at the bottom, so that element does most of the reheating after showers. It also sits in the sediment, and HomeGuide notes that sediment at the bottom of the tank corrodes the lower element. If one element is going to fail first, it's usually that one.

Likely causes, most common first

1. 1

   Cause 1: A burned-out element

   This is the big one. An element that has opened up inside won't heat at all. State's service handbook lists a burned-out element as a standard cause of no hot water and tells techs to confirm it with a continuity or amperage check. The test is quick and needs only a cheap meter. Our water heater element test page walks through it.

2. 2

   Cause 2: A grounded element

   Sometimes the element sheath cracks and the coil touches the tank. That can trip the breaker, and it can also keep the element heating when it shouldn't. State's chart lists a grounded element as a cause of water that's too hot, and A.O. Smith says a grounded element is a common reason the red reset button trips.

3. 3

   Cause 3: A bad thermostat

   A thermostat that won't close keeps its element cold. One stuck closed keeps heating until the high-limit switch trips. State's troubleshooting chart lists "thermostat stuck in call for heat" as a cause of water that's too hot. See our water heater thermostat guide for settings and testing.

4. 4

   Cause 4: Tripped high-limit (ECO)

   The ECO (energy cut-off) is the red reset button above the upper thermostat. State's handbook says it cuts power to the elements if the top of the tank reaches 180°F, on the models that handbook covers. It doesn't trip for no reason, so treat a trip as a symptom, not the fault. Our reset button page covers what to do.

5. 5

   Cause 5: Scale buried on the element

   In hard water, scale forms on elements and makes crackling, popping or hissing sounds, according to A.O. Smith, which suggests cleaning the elements or replacing them if they're heavily coated. A scaled element works harder and dies sooner. If your tank sounds like a coffee percolator, see water heater noises.

Element or thermostat? How to tell

Test the elements first. They're the part that fails most, and the test is done with the power off. If both elements read correctly and neither is grounded, the thermostat moves to the top of the list.

Bradford White's procedure for that is live: a technician checks for voltage across specific thermostat terminals with the tank cold. That means working on a powered circuit. If you aren't comfortable working near live terminals, stop at the element test and call a pro. Plenty of experienced DIYers do exactly that.

Picking a replacement element

Elements aren't one-size-fits-all, but they're close. Match three things to the old part:

The rating plate on the side of the tank lists the element wattage and voltage. A common rating is 4500 watts at 240 volts, which pulls about 18.75 amps and measures about 12.8 ohms cold. That's the "4500w heating element" you'll see on store shelves.

Element sheath material matters more than people think. Hard-water homes usually do better with a low-watt-density or stainless element, which spreads the same heat over more surface and scales more slowly. It costs a little more and usually lasts longer.

Every electric water heater element is an immersion (submersible) element. It has to be fully under water when it's powered. If it runs in air, even briefly, it can burn out. Bradford White calls this dry firing and says it can make the element inoperative.

Fixes you can do

• Replace a dead element: drain the tank below the element, unscrew it, fit a new gasket, refill, then restore power. Full steps are on how to replace a water heater element.
• Clean or replace a scaled element. It's the same job. Once it's out, a heavily crusted element is cheaper to replace than to scrape.
• Flush the tank once a year. HomeGuide says yearly flushing extends the heating element's lifespan. See how to drain a water heater.
• Fix a leak at the element. A.O. Smith says leaks around elements come from failed gaskets, and if tightening the element doesn't stop it, replace the element.

When to call a pro, and what it costs

Call a plumber or electrician if the breaker trips again right after you reset it, if the ECO keeps tripping, if you see scorch marks on the wiring, or if you just don't want to open the electrical covers. That's a fair call.

HomeGuide puts a heating element replacement at $100 to $350 and a thermostat replacement at $100 to $350, parts and labor. Standard tank repairs in general run $150 to $700. On an old tank with a rusty base, put that money toward a new heater. Compare it with water heater repair cost before you decide.