Thermostat & Heating Element Replacement

Last updated September 24, 2026

Most electric water heater problems trace back to one of two parts: a heating element or a thermostat. Both are common, generally straightforward repairs, but figuring out which one is failing takes a bit of diagnosis.

How to tell which one is the problem

A failed upper element usually means no hot water at all. A failed lower element more often means water that starts hot and runs out quickly. A faulty thermostat can look like either, or cause inconsistent temperatures rather than an outright failure.

Why elements fail sooner in hard water

Mineral scale from Colorado's hard water builds up directly on the heating element surface, insulating it and forcing it to work harder, which shortens element life compared to a soft-water climate.

What not to do yourself

Electric water heaters run on 240-volt circuits. Testing or replacing an element or thermostat involves working inside an energized electrical panel on the unit, this is not a job to do without disconnecting power correctly and confirming it's off, which is why we leave this one to a technician.

How the repair is done

Power to the unit is shut off and confirmed off, the access panel is removed, the specific component is tested, and the failed part is replaced. Most element and thermostat replacements are completed in a single visit.

Upper versus lower element symptoms in more detail

An upper element failure typically means no hot water at all, since the upper element heats first. A lower element failure more often means an initial burst of hot water that runs out faster than expected, since the lower portion of the tank stays cooler.

If Problems Keep Recurring

Elements and thermostats that fail repeatedly on the same unit can sometimes point to underlying sediment buildup insulating the tank, see our noisy water heater & sediment page for that connection.

How Elements and Thermostats Work Together

Electric water heaters typically have an upper and a lower element, each controlled by a thermostat mounted against the tank. The upper thermostat has priority and contains the high-limit safety switch. When the upper portion is hot, it passes power to the lower thermostat, which heats the rest of the tank.

Symptoms of a Failed Element or Thermostat

No hot water usually points to the upper element or thermostat, or a tripped high limit. Hot water that runs out quickly suggests the lower element or thermostat has failed. Water that's too hot can mean a stuck thermostat, a potential safety issue.

Testing Safely

Testing requires working near 240 volts. With the power off, a technician checks element resistance with a meter; a typical 4,500-watt element reads around 12 to 13 ohms. With power on, voltage checks at the thermostats show whether they're passing power. These steps should be done by someone trained in electrical safety.

Choosing Replacement Elements

Replacement elements must match the tank's voltage and wattage. Low-watt-density elements last longer in hard water because they run cooler and resist scale. Screw-in elements are most common; some older tanks use bolt-on flanged elements.

Replacing an Element

Turn off the breaker and verify power is off, drain the tank below the element, remove the element with a socket wrench, install the new one with a new gasket, refill the tank completely and then restore power. Energizing a dry element destroys it.

Hard Water and Repeated Failures

If lower elements keep failing, sediment is likely burying them. Regular flushing prevents repeat failures.

A Typical Colorado Repair

A family in a Pueblo West home with an electric water heater notices hot water runs out halfway through the second shower. The technician tests the lower element and finds it open, with heavy scale when removed. The tank is drained, a low-watt-density replacement element installed, and the tank flushed while it's empty. The lower thermostat tests fine. After refilling and restoring power, both elements heat properly. The technician recommends flushing every six months given the area's hard water.

Upper Thermostat and High-Limit Trips

If the high-limit reset button keeps tripping, the cause could be a thermostat stuck closed, an element shorted to the tank, or loose wiring. Simply resetting it repeatedly isn't safe; the underlying problem needs diagnosis.

Questions Homeowners Ask

How long do elements last? Often several years, less in hard water.

Should I replace both elements at once?

Can I raise the thermostat to get more hot water? Raising it increases scald risk and scale; better to address the underlying cause.

Why Elements Fail in Colorado

Most element failures in Colorado come from scale. Hard water deposits minerals directly on the element's hot surface and settles sediment around the lower element. Scale insulates the element, making it run hotter until its sheath cracks and it shorts or burns open. Dry firing, energizing an element when the tank isn't full, is another cause, usually after draining a tank for service. Voltage problems, such as a loose connection, can also burn terminals.

Choosing Thermostat Settings

Most electric water heaters have separate upper and lower thermostats, both typically set to the same temperature, around 120°F. Setting the lower thermostat higher than the upper can reduce recovery at the top of the tank. Setting both higher increases scald risk and scale. Anti-scald mixing valves allow higher storage temperatures with safe delivery.

Electrical Safety Checks

During an element or thermostat replacement, a technician should inspect wiring for heat damage, tighten connections, confirm correct breaker size and wire gauge, and replace insulation and covers.

When Replacement of the Whole Heater Makes More Sense

If an electric tank is past about ten to twelve years, leaks, or has repeated element failures from heavy scale, replacing the whole unit may be better value than replacing parts. A new tank with low-watt-density elements, a brass drain valve and a flush schedule avoids repeating the same problems.

Anti-Scald Protection

Households with young children or elderly residents benefit from an anti-scald thermostatic mixing valve, which lets the tank store water hotter while delivering safe temperatures at taps.

Element Replacement Timing

If one element fails from scale, the other may follow soon; inspecting both during the visit is efficient. Many technicians replace both elements and flush the tank in one visit.

Testing After Replacement

After replacing parts, a technician confirms both elements heat and the thermostats cycle correctly.

Testing Before Replacing

With power off at the breaker and confirmed off with a meter, each element can be tested for resistance: a 4,500-watt, 240-volt element should read roughly 12 to 13 ohms. A reading of zero or infinity means the element has failed, and any continuity to the tank body means it's shorted.

Thermostats are checked next. The upper thermostat controls power to both elements in sequence, so a failed upper thermostat can leave the whole tank cold even with good elements. Replacing like-for-like parts and matching the original wattage keeps the circuit within its rating.