Electric Water Heater Not Heating? Causes, Reset Button, When to Call

Quick answer

If an electric tank water heater gives no hot water at all, the usual causes are a tripped breaker, a tripped high-limit reset button (the ECO), or a failed upper element or thermostat. If the water is lukewarm or runs out fast, look at the temperature setting, more demand than the tank can supply, sediment, or a failed lower element. Start with the breaker and the setting. Parts behind the access panels sit next to live high-voltage terminals, and manufacturers want a qualified person to find the cause there.

First: no hot water, or not enough?

Run a hot tap for a minute and see which pattern fits.

What you notice	Likely causes the manufacturers list	Start with
No hot water at all	No power, a tripped ECO, a failed upper element or upper thermostat	Steps 1 and 3
Hot water runs out fast	Demand above capacity, a failed lower element, sediment, low settings	Steps 2, 4, 6
Lukewarm at every tap	Low settings, a failed lower element, very cold incoming water	Steps 2 and 5
Lukewarm at one fixture only	A faulty mixing valve in that fixture	Step 5
Much slower to reheat than before	Sediment or lime on the elements, a thermostat problem	Step 6
Water too hot, or relief valve discharging	A thermostat or element fault, high pressure, thermal expansion	Call a pro

Causes involving an element, a thermostat, or the ECO need a technician to confirm. Source: Bradford White service manual 238-51544; A. O. Smith and State use and care guide 100309904; Rheem use and care manual AP23124

How a two-element tank heats

Most electric water heaters have two thermostats behind an upper and a lower access panel (CPSC), each controlling its own heating element near the top or bottom of the tank. Bradford White’s service manual describes the usual sequence, with one element on at a time: the upper element heats the top of a cold tank first, then power switches to the lower element for the rest. Cold water enters at the bottom as you use hot water, so the lower element cycles most often.

That sequence explains the two patterns:

• No hot water at all often traces to the upper side, because the lower element gets power only after the top is hot. A. O. Smith lists a burned-out upper element and a broken upper thermostat among the most likely causes.
• Some hot water, but less than before points to the lower side. The lower element does most of the work, so it usually wears out first, and a failed one still leaves some hot water (A. O. Smith).

These are causes to describe to a technician. Testing or replacing an element means working on live electrical parts.

1. Check the breaker and any disconnect switch

Rheem’s troubleshooting chart includes these power causes: a blown fuse or tripped breaker, a disconnect switch that is off, and a utility outage.

1. Find the water heater’s breaker. If it has tripped, switch it fully off, then back on, once.
2. If there is a disconnect switch on the wall near the heater, make sure it is on (Rheem).
3. If your area has lost power, contact the electric utility.

If the breaker trips again, stop. An element shorted to ground usually trips the breaker, according to Bradford White’s service manual, and A. O. Smith says a qualified person should check the wiring or breakers if the heater isn’t getting power.

Then give it time. A tank of cold water can take several hours to heat. If there’s still no hot water after two hours, keep troubleshooting (A. O. Smith).

2. Check the temperature setting

Measure first. CPSC suggests a candy or meat thermometer under the faucet, first thing in the morning or at least two hours after anyone used hot water. Check several taps to rule out a problem in one faucet or shower control (A. O. Smith).

What it should be. CPSC urges setting water heaters to 120°F, and DOE’s Energy Saver guide calls 120°F safe for most of the population. Bradford White and A. O. Smith ship their thermostats at about 120°F, and Rheem calls its factory setting of 120°F or less the recommended starting point.

Where the controls are:

• Digital control on the front. Rheem’s electric models with an electronic control are set from 110°F to 150°F on the control itself. Rheem warns not to try setting the temperature by removing the control or the lower access panel.
• Dials behind the panels. On standard models, both thermostats must be set to the same temperature (CPSC). The dials sit right next to live terminals, so Rheem and Bradford White describe adjusting them only with the breaker off and the plastic protective cover in place. Your electric utility may do it for you, some at no charge (CPSC). If you aren’t comfortable working there, leave it to the utility or a technician.

Going above 120°F? A. O. Smith says thermostatic mixing valves at each faucet are particularly important if you do, and Rheem notes that homes with small children, disabled, or older adults may need 120°F or lower. If your dishwasher leaves grit on dishes, see why water temperature matters for a dishwasher.

3. The red reset button (ECO or high limit)

What it is. The energy cut off (ECO), or high limit, is a safety switch with a red reset button, mounted above the upper element against the tank (Rheem) or on the upper thermostat (A. O. Smith). If the water gets too hot, it cuts power to the elements and stays off, with no hot water, until someone resets it by hand.

Why it trips. In most cases the tank overheated because an element or thermostat failed (A. O. Smith). Repeated trips usually come from an element shorted to ground (Bradford White service manual). The button is a symptom, not the fault.

What the manufacturers say about resetting:

• Rheem describes pressing the red button with the power off and the plastic protective cover left in place, but says a qualified service technician must find and correct the cause before the heater goes back into service.
• A. O. Smith and State (the same guide is posted on both sites) say a qualified person should find and repair the cause, and the power should stay off until that is done.
• Bradford White gives no homeowner reset steps: if overheating occurs, turn off the power and contact a qualified service technician.

Bottom line: the safest move is to leave the breaker off and book a technician. If the button has already been reset and the hot water quits again, don’t keep resetting it. On Rheem electronic-control models, a service light blinking red four times can mean a tripped ECO, or a wiring or element fault that needs service.

4. Running out fast: demand versus first-hour rating

Rheem and Bradford White both list demand beyond the heater’s capacity as a cause; Rheem says to wait for the heater to recover.

The number to check is the first-hour rating: how many gallons of hot water a heater can supply in an hour, starting with a full tank (DOE). It appears in the top left corner of the EnergyGuide label as “Capacity (first hour rating),” and DOE recommends a rating that at least matches your home’s busiest hour of use.

Use	Average gallons of hot water per use
Shower	20
Shaving	2
Hand dishwashing or food prep	3
Automatic dishwasher	7
Clothes washer, top-loader	25
Clothes washer, front-loader (H-axis)	15

DOE calls these estimates based on averages. Multiply each use by how often it happens in your busiest hour, then add them up. Source: U.S. Department of Energy, Sizing a New Water Heater (archived June 10, 2026)

For example, 2 showers (20 gallons each) plus a front-loader load (15 gallons) in one hour add up to 55 gallons, so that home needs a first-hour rating of at least 55 gallons. If your label’s rating is lower than your busiest hour, running out is expected, not a fault.

If your busiest hour is bigger than the rating:

• Use less hot water. A. O. Smith suggests washing clothes in cold water, flow restrictors on showerheads, and fixing leaky faucets. For more ways to cut water heating costs, see how to lower your electric bill.
• Consider the heater’s age. A. O. Smith suggests a larger model if the heater is old, and DOE says most storage water heaters last 10 to 15 years. If yours is in good shape, mixing valves plus a higher setting may stretch your hot water (A. O. Smith).

5. Lukewarm in winter, or only at some taps

• Cold weather. Colder incoming water in winter takes longer to heat, and Rheem calls this normal.
• One shower or faucet only. A failed mixing valve, built into many shower controls, can cut the hot water at that fixture even with a full tank (A. O. Smith).
• A hot tap left open or leaking. Make sure all faucets are closed (Rheem). Even a small leak on the hot side can make the heater seem weak, A. O. Smith notes.
• New installation. Reversed hot and cold connections, or a dip tube that melted because pipes were soldered while attached to the heater, usually show up soon after installation (A. O. Smith). The installer or a plumber should correct these.

6. Sediment and mineral buildup

Minerals in tap water form lime on the elements and sediment at the bottom of the tank, more so with hard water, A. O. Smith explains. Sediment impedes heat transfer and lowers efficiency (DOE), and Bradford White’s service manual traces slow recovery to sediment or lime around an element. A rumbling noise points to scale on the elements (Rheem); singing or hissing elements point to lime (Bradford White).

Draining some water through the drain valve flushes sediment, but the recommended schedules differ:

Source	Recommended draining
Rheem	A few quarts monthly
Bradford White	Monthly, until the water runs clear
DOE	A quart every 3 months
A. O. Smith	A drain and flush after the first six months, then at least yearly

Follow the schedule in your own heater's manual. Source: Rheem AP23124; Bradford White 238-44422; DOE Energy Saver guide (2022); A. O. Smith 100309904

Before you drain:

• Shut off the power first, and remember the water can scald (Rheem).
• Never restore power until the tank is completely full (A. O. Smith, Bradford White). An element that heats without water around it (dry firing) burns out.
• Sediment can harden into masses that block draining, and a qualified person should remove them (A. O. Smith). Cleaning lime off elements means removing them, which is technician work.

Water too hot, or the relief valve is discharging

A small drip from the temperature and pressure (T&P) relief valve’s discharge pipe usually means your home’s water pressure is too high or you need a properly sized and pressurized expansion tank, according to A. O. Smith. A large amount of hot water may mean the tank is overheating; turn the power off until it is fixed. Rheem calls a popping or draining relief valve an unacceptable condition for your water supplier or a plumbing contractor to correct. Never plug the valve.

Bradford White recommends a yearly inspection by a qualified service technician. To estimate what your water heater costs to run, try the appliance cost calculator. For the limits of what this site covers, see the safety disclaimer.