Quick answer
An electric water heater that trips the breaker most often has a heating element whose metal sheath has cracked, letting water reach the live wire and short it to the tank. Other causes are a thermostat with welded contacts, a loose or burnt wire at the terminals, water dripping onto the wiring, or a worn 30-amp double-pole breaker. Leave the breaker off until the element and wiring are tested.
When an electric water heater is tripping the breaker, the breaker is doing its job: something downstream is pulling more current than the circuit is rated for, or current is leaking to ground. The usual suspect is cheap and quick to replace, but you cannot tell which fault you have by looking, and resetting the breaker over and over is how a small fault becomes a scorched panel.
The most common cause: a shorted heating element
A residential electric tank has two elements — 3,000 watts each on many Canadian-market tanks, 4,500 on others — on a 240-volt circuit protected by a double-pole breaker sized to the element rating. Each element is a resistance wire packed in insulation inside a copper or stainless sheath. After years of heating cycles — and especially when sediment buries the lower element and makes it run hotter than designed — the sheath cracks. Water gets in, the element shorts to the tank, and the breaker trips the instant that element energizes.
This is why the timing of the trip is the best clue you can give a technician. A breaker that trips within seconds of being reset points at a dead short: a failed element or a wire touching the tank. A breaker that holds for twenty or thirty minutes and then trips points at an overload or heat problem: a weak breaker, a loose connection heating up, or a thermostat that is not switching off.
Other reasons an electric water heater trips the breaker
- Thermostat with fused contacts. The upper and lower thermostats are simple mechanical switches; when the contacts weld closed, both elements can end up running at once, drawing more than the circuit allows. The tank also runs hotter than its setting and the red high-limit (ECO) button may pop too.
- Loose or burnt terminal connections. A screw terminal that has worked loose arcs, chars the insulation and can bridge to the tank jacket. Look for discolouration at the element terminals or the breaker lug — never touch them with the power on.
- Water on the wiring. A weeping element gasket or a drip from the T&P relief valve above the access panel gets the terminals wet. Dry it, fix the drip, and you have found the cause.
- A tired breaker. Breakers wear with every trip and lose their rated capacity. If the elements and wiring test clean, the breaker itself is the last suspect, and that job belongs to a licensed electrician.
- Wrong breaker or element after a previous repair. A tank with 4,500-watt elements belongs on 10-gauge wire and a 30-amp breaker, while 3,000-watt elements run on a 20-amp circuit; put 4,500-watt elements on the smaller circuit, or an undersized breaker on the bigger tank, and it trips under perfectly normal load. The rating plate on the tank settles which you have.
What you can safely check yourself
- Leave the breaker off. Do not keep resetting it — each reset with a dead short stresses the panel and the wiring.
- With the breaker off, remove the upper and lower access panels on the tank and fold back the insulation. Look for moisture, rust streaks or scorched wiring. If you see any, stop and call.
- Press the red reset button on the upper thermostat. If it clicks and the breaker holds afterward, the high-limit tripped for overheating, which is a thermostat problem to have looked at rather than a fix.
- Leave the meter work to a technician. Testing an element means checking its resistance (roughly 12–13 ohms for a 4,500-watt element, closer to 19 for a 3,000-watt one) and confirming no continuity to the tank; a reading near zero or a path to ground means it has failed.
- If the breaker holds but the water is only lukewarm, the lower element has probably burned out rather than shorted — see why a water heater stops producing hot water.
What the repair costs
A failed element is a routine, same-visit repair: heating elements run $200–$400 replaced, and the diagnostic service call of $90–$150 folds into the work if you proceed. Thermostats sit in the same range. If the tank is past 8–12 years, the elements have been buried in sediment for a long time, and the jacket is rusting at the fittings, a new electric tank at $1,200–$2,500 installed is the better use of the money — see our water heater repair vs. replacement analysis.
Where electric water heaters show up around Burlington
Most detached homes in Burlington, Oakville and Hamilton heat water with natural gas, so electric tanks are the minority — but they are the norm in specific places. Rural addresses north of Dundas Street in Kilbride, Lowville and Carlisle without gas service run electric or propane. Condos and fan-coil apartments along Lakeshore Road and in downtown Burlington often have an electric tank in a closet. And a growing number of homes that switched from a furnace to a cold-climate heat pump are going all-electric, with an electric tank or a heat pump water heater to match.
In all three cases, sediment from moderately hard lake or well water is what cooks the lower element first, and a flush every year or two is the cheapest insurance you can buy for an electric tank.
ZK Mechanical repairs and replaces electric and gas tanks across Burlington, Oakville and Hamilton, and our technicians carry common elements and thermostats on the truck. If the breaker has tripped twice, stop resetting it and book a repair, or see our water heater service page for what a visit includes.