Can I splice these two gages of electrical wire together and be reasonably safe?
Do NOT use the 18 gauge wire. As some of the other answers said, this is NOT safe. 18 gauge wire cannot support the current that 10 gauge can. The water heater can draw as much as 40 amps on 10 gauge conductors. This is what the NEC rates as the maximum amount of current on wires that large, and these ratings havn’t changed much over the years. It sounds kinda funny that 10 gauge wires are used to power a 1500W/120V element. Unless there are two elements that would be simultaneously powered, I’m surprised that you havn’t burned out the element. 1500W for heating 19 gallons kinda sounds weak. I’d expect a 4500W element or two elements. Anyway, do not use the 18 gauge plug. BIG trouble. If you must use a plug, use one that can support up to 40 amps and wire the female end of that plug ALSO with 10 gauge wires. ALSO, it’s wise that the circuit breaker that powers that circuit matches the ampacity rating of the wires (40 A). Next, are you sure that your water heater is a 120V device? Are o
