1) Turn off power before touching water heater that is shorting or wet or was flooded.
2) Circuit breakers & fuses blow because of heat. A short will cause heat. Tighten screws on terminals inside box, listen for crackling sound/burning smell from loose-fitting parts.
3) Easy test for circuit breakers: move water heater wires to another same-size breaker. If same-size does not blow, then problem is breaker.
4) A short between fuse box and water heater could be gnawed electrical wire. Inspect wire.
5) Wires have size markings. 5500 watt water heater needs #10 wire. 4500 watt water heater needs #10 wire but can work with smaller #12 if distance is not long. See label on side of heater for wattage, voltage, etc. Element wattage is water heater wattage even with 2 elements.
6) Short inside water heater can be elements or thermostat. Open covers and inspect parts for burning. Screws should be very tight against copper wire. Sediment could fill bottom of water heater cause lower element to short.
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