Quick answer
An electric water heater that is not heating has usually lost power or lost an element. Check the double-pole breaker, then the red ECO reset on the upper thermostat. No hot water at all points to the upper element or thermostat; a short supply of hot water points to the lower element. A good 4,500-watt element reads about 13 ohms.
Your electric water heater is not heating because one link in a short chain has opened: the breaker, the high-limit reset, a thermostat or an element. There is no flame, vent or gas valve to consider, which makes an electric tank the easiest water heater to diagnose with a meter. The pattern of the failure tells you where to look before any panel comes off.
No hot water at all versus hot water that runs out fast: how the two thermostats take turns
The two elements do not share the work equally, so each one fails with its own symptom.
- No hot water at all: the breaker has tripped, the ECO has opened, or the upper element or upper thermostat has failed.
- A few minutes of hot water, then cold: the lower element or lower thermostat has failed, and only the top third of the tank is being heated.
- Lukewarm water that never gets properly hot: an element is partly failed or a thermostat is out of calibration.
- Water far too hot, then nothing: a stuck thermostat or grounded element overheated the tank and tripped the ECO.
A standard two-element tank never runs both elements at once. The upper thermostat has priority: it powers the upper element until the top of the tank reaches temperature, then switches the supply down to the lower thermostat, which runs the lower element to heat the rest. The lower element does most of the daily work. That sequence explains the symptoms: if the upper element is open, the upper thermostat is never satisfied, power never passes to the lower half, and the whole tank stays cold even though the lower element is fine.
Check these yourself first
- The breaker: a double-pole breaker, usually 30 amps, with two handles tied together. Push it fully off, then on. A breaker that trips again stays off, for the reasons in why a water heater trips the breaker.
- The ECO reset: with the breaker off, remove the upper access panel and press the red button on the upper thermostat. The full procedure is in how to reset a water heater.
- Demand: a houseful of guests or a new soaker tub can empty a healthy tank. Give it two hours with no use and test again.
- Leaks: water at the element gaskets or inside the lower panel means stop and call.
Anything beyond the reset button involves live 240-volt terminals. That is where homeowner checks should end.
The element continuity test: about 13 ohms for 4,500 W
An element is a resistor, and its wattage tells you what it should read. With the breaker off, the power confirmed dead and both wires lifted from the element, a meter across the two screws should show the following.
- 4,500 W element at 240 V: about 13 ohms.
- 3,000 W element at 240 V: about 19 ohms.
- An open reading with no continuity: the element has burnt through and is replaced.
- Any continuity from either screw to the metal tank: the element is grounded. It can heat with the thermostat open, so it is replaced even if it still works.
Thermostats are checked live, by following voltage through them in sequence, which is why that half of the job belongs to a technician.
Dry-fired elements after a refill
The fastest way to kill a new element is to power it in air. After a tank has been drained for a move, a repair or a new installation, the breaker has to stay off until a hot tap runs a full, steady stream with no sputtering. An upper element energized in an air pocket burns out almost at once, and the tank then behaves exactly like one with a failed upper element: stone cold. Scale does a slower version of the same thing to the lower element, where hard water in Halton and Hamilton, and well water on rural lots, buries it in mineral sediment until it overheats.
Element and thermostat replacement weighed against tank age
- Diagnostic visit: $90–$150, taken off the repair bill.
- Heating element replaced: $200–$400.
- Other electric tank repairs, thermostats included: within $150–$800.
- New tank installed: $1,200–$2,500.
The rule: under 8 years old with a dry, rust-free tank, replace the part. Past 10 to 12 years, or with rust at the element ports or an element that will not unthread, put the money toward a new tank, because the second element and both thermostats are the same age as the part that just failed. Electric tanks are the norm in condos and on rural lots where gas mains do not reach, such as Kilbride, Lowville and rural Flamborough.
ZK Mechanical repairs and replaces electric tanks across its service area, including electric water heater repair in Burlington. See water heater service or get in touch; the phone is (647) 801-1252.