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This article describes how to test electric hot water heater heating elements, what readings to expect if using an ohmmeter.

This article describes the steps in testing electric hot water heater heating elements, followed by a guide to replacing a bad heating element (Electric Water Heater Element Replacement). This series of articles describes how to inspect, operate, diagnose, and repair electric hot water heaters. The articles at this website will answer most questions about electrical water heaters as well as many other building plumbing system inspection or defect topics. Reproduction of this web page electronically at other websites is prohibited. If you cannot find information you need here or if you have comments, questions, suggestions for inspecting and diagnosing water heaters Contact Us

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How to Test Electric Water Heater Heating Elements

Because the electric water heater might be failing to work due to loss of electrical power to the unit, or because of a malfunctioning high-temperature cutoff switch, you should also see the test steps at How To Test High Temperature Cutoff Switch

Electric water heater drawing (left) showing the sequencing procedure for electric water heater elements is provided courtesy Carson Dunlop Associates, used with permission

Electric water heaters have two heating elements - thick metal loops that get hot when electricity flows through them, similar to the burner on an electric range.

The lower heating element heats cold water as it enters the hot water tank. (Incoming cold water is delivered to the bottom of the tank through the dip tube.)

This element works the hardest, is on the most, and so often is the first to burn out. The upper heating element acts as a "booster" to heat water when there is a high demand. This element heats only the water in the upper portion of the hot water tank.

As we introduced earlier, if there is some hot water but it is limited in quantity or temperature, just one of the heating elements may have failed.

Scale coating a water heater element can also reduce the quantity of hot water (or cause heating element failure) - a topic we review in more detail at WATER HEATER SCALE - De-Liming Procedure and WATER HEATER SCALE PREVENTION and at WATER HEATER NOISES.

If the electric water heater produces the same old quantity of hot water, but water is only tepid rather than hot, we suspect that the top water heater element has burned out. The bottom element is heating the entire tank but it is not capable of heating the water to the same high temperature as if both elements were working. Long tepid shower - bad top water heater element.

If the electric water heater produces the same old hot water temperature, but the quantity seems drastically reduced, we suspect that the bottom water heater element has burned out. Only the water in the top of the tank is being heated. Cold water enters and remains at the bottom of the water heater. So our hot water is plenty hot but we run out in just a few minutes. Short hot shower - bad bottom water heater element.

As we're about to show in detail, one can test a water heater heating element by a simple procedure using a continuity tester or a volt-ohm meter- a VOM. For details on how to use electrical test equipment see Using DMMs & VOMs Safely and see Voltage Measurement & Detection. General electrical inspection safety advice is at SAFETY FOR ELECTRICAL INSPECTORS.

Steps in Testing an Electric Water Heater Heating Element - Good Method

1. Turn off electrical power to the water heater - you should have done this earlier if you read the instructions above. Turn off power at the water heater circuit at the main electrical panel.
2. The water in the heater should be lukewarm or colder. If the water heater is hot, run hot water in the building (with the water heater electrical power OFF) until water flows lukewarm or colder.
3. Disconnect the electrical wires at the heating element terminals. (This is so whether testing upper or lower heating element).
4. Test for current flow: Use a VOM, DMM, or Ohmmeter or multimeter set to read "resistance" or "ohms" as follows: connect one alligator clip or touch one probe of the VOM to each terminal on the water heater element.
   
   One probe touches one terminal, the other probe touches the other terminal. If the Ohmmeter needle doesn't move (or no reading is given on the DMM) then the electric water heater heating element is defective and needs to be replaced.
   
   If the ohmmeter needle moves or you get some Ohm reading (other than infinity) then the heating element is OK and you are ready to test the other heating element on the heater. In sum, if there is "continuity" through the heating element it is working. If there is no continuity (no electrical current can flow) then the element has failed.

Testing an Electric Water Heating Element for a Short Circuit - Crude Method & OHM Table for Water Heater Elements

We do not usually make this test but we include it here as it appears in some diagnostic procedures for electric water heaters. The water heater element OHMS chart (left, courtesy A.O. Smith) describes the actual ohm reading you'd expect if testing a factory OEM heater element of the wattage shown.

Even without that level of detail there is a simple test you can perform to see if an electric water heater heating element is in good working order:

1. Turn off electrical power to the water heater - you should have done this earlier if you read the instructions above. Turn off power at the water heater circuit at the main electrical panel.
2. Remove the access panel cover and insulation from the top or bottom water heater element (described above)
3. Connect the alligator clip or test terminal of your continuity tester to one terminal of the heating element. That's the wire and screw right on the heating element itself.
4. Connect the other probe of the continuity tester (or VOM) to a bolt or bracket that holds the heating element in position.
5. If the test light goes on, the buzzer sounds, or your VOM (set to Ohms) indicates continuity, there is a short circuit in the heating element and it needs to be replaced.

Causes of Heating Element Failure on Electric Water Heaters

Besides old age and high usage, if your building water supply provides hard water (high in mineral content), scale build-up on water heater elements can lead to their demise.

See WATER HEATER NOISES for details about removing scale from a water heater.

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ELECTRIC WATER HEATERS
  Identify Electric Water Heater Parts
  Electric, Gas, Oil Water Heater Efficiency
  Electric Water Heater Checklist
  Electric Water Heater Controls List
  Water Heater Anode & Dip Tube Check
  Hot Water Temperature & Pressure Valve
  Electric Water Heater Repair Guide
  Electric Water Heater Reset Switch
  Electric Water Heater Thermostats
  Electric Water Heater: No Hot Water
  Electric Water Heater Reset & Temp Set
  Test Electric Water Heater High Temp Cutoff
  Test Electric Water Heater Elements
  Timers for Electric Water Heaters
  Replace Electric Water Heater Element
  Drain a Hot Water Heater Tank

• Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.

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