Shut off the breaker, confirm the power is dead with a voltage tester, disconnect one wire from the element and read resistance across its two screws. A. O. Smith says 5 to 25 ohms is good, with 12.5 typical. Then test each screw to the tank: anything but OL means a shorted element.
Should you test the element at all?
Test if your heater is electric and you have no hot water, lukewarm water, or hot water that runs out fast. Gas water heaters don't have elements, so this page doesn't apply to them. A standard electric tank has two elements, one near the top and one near the bottom, each controlled by its own thermostat. Either one can fail on its own.
If your heater is running out of hot water fast, the lower element is a prime suspect. If you have no hot water at all, start with the checks on why you suddenly have no hot water, since a tripped reset button or breaker is much quicker to rule out.
One honest note before you start. Rheem's manual tells owners not to attempt repair of electrical wiring, heating elements or other safety devices, and to refer repairs to qualified service personnel. Testing an element to find out what's wrong is one thing. Replacing it, or working on the thermostat or wiring, is a job many homeowners leave to a plumber. Use this page to learn what's failed, and decide from there.
How do you shut the power off safely?
Water heater elements run on 240 volts, which is enough to seriously hurt you. Follow this order.
- 1Turn off the breaker for the water heater.
- 2Confirm the power is off with a voltage tester. A. O. Smith's installation guide warns that circuit breakers can be mismarked, so it says to always check the incoming power wires with a voltmeter instead of trusting the panel label.
- 3Open the access panel on the side of the tank, then move the insulation and the plastic safety cover aside.
- 4Test the wires at the element with the voltage tester before you touch them. Proceed only when it reads zero volts.
Rheem's manual says to turn off the breaker if a heater has been overheated. If the panel, the wires or the thermostat look burned or melted, stop and call someone. That's beyond a simple element test.
How do you read the two element tests?
### The resistance test
Do this with the power confirmed off.
- 1Label and disconnect the wires from the two screw terminals on the element you're testing. Take a phone photo first.
- 2Set the multimeter to its lowest resistance (ohms) setting.
- 3Touch one probe to each of the two screws.
- 4Read the number and write it down.
A. O. Smith's guide says an element reading between 5 and 25 ohms is good, and 12.5 ohms is typical. Outside that range, it says to replace the element.
You can also work out what your element should read. Resistance equals voltage squared divided by wattage. The wattage is stamped on the element, and Rheem lists 4,500 and 5,500 watts as loads for its electric heaters. At 240 volts, a few example wattages work out like this.
| Element wattage | Expected resistance at 240 volts |
|---|---|
| 3,800 watts | about 15.2 ohms |
| 4,500 watts | about 12.8 ohms |
| 5,500 watts | about 10.5 ohms |
If your reading is way off the calculated figure, or the meter says OL or zero, the element is bad.
### The ground test everyone skips
An element can read fine across its screws and still be bad, because its internal coil can touch the metal sheath and leak current into the tank. That's called a shorted or grounded element, and Lennox lists a shorted element among the most common reasons a water heater trips its breaker.
A. O. Smith's test: with the power off and both wires disconnected, set the meter to its highest resistance setting. Touch one probe to a screw terminal and the other to bare metal on the tank or the thermostat bracket. Repeat for the second screw. The meter should read OL. Any lower reading means the element is shorted to ground, and it needs to be replaced. Do this for both elements. If your breaker keeps tripping, read why an electric water heater keeps tripping the breaker.
### What do the readings mean?
| Reading | What it means | Next step |
|---|---|---|
| 5 to 25 ohms across the screws, OL to ground | Element is good | Look at the thermostat, reset button and power supply |
| OL or infinity across the screws | Element is open, burned out | Replace the element |
| Zero or near zero across the screws | Element is shorted | Replace the element |
| Any reading from a screw to the tank | Element is grounded | Replace the element, and stop using the heater |
What if both elements test good?
Then the problem is somewhere else in the chain. A. O. Smith's guide walks through it in order:
- Press the red reset button on the upper thermostat. If it clicks, the water got hot enough to trip the energy cutoff. Rheem adds that the cause of a high-temperature trip must be investigated by a qualified service technician before the heater goes back into service.
- Have a technician check for 240 volts at the top two screws of the upper thermostat. A. O. Smith lists this as a step, but it's a live test on an open 240-volt circuit, so it's where a homeowner should stop and call a pro. If there's no 240 volts, the problem is the breaker or the wiring.
- Suspect the thermostat. If both elements are good and the heater runs constantly or not at all, A. O. Smith says the thermostat contacts may have welded shut, and that the lower thermostat is the most likely to fail because it does most of the work.
- Look for a leak on the hot side of the plumbing, since a slow leak drains hot water constantly.
What does replacing an element involve?
Replacing an element means draining the tank, unscrewing the old one with an element wrench, and installing a new one that matches the wattage and voltage on the rating plate. A. O. Smith's guide also says the tank must be completely full before power is connected, because running the heater dry burns out the upper element.
Scale matters here. Rheem's manual lists a rumbling noise as a sign that mineral deposits have built up on the heating elements, and says the elements should be removed and cleaned. Phoenix water is hard, so it's worth knowing that flushing is part of A. O. Smith's annual maintenance checklist. Our page on how often to flush a water heater in Phoenix gives a schedule for hard water.
If the tank is old, the element may not be the only thing worth fixing. Our page on whether to repair or replace a water heater covers that decision.
HQ Plumbing and Air is licensed and insured and takes emergency calls 24/7. We give free estimates and an upfront price before work starts, so you'll know the cost of a diagnosis and repair before we begin.