Hi, trying to replace thermostat on my copper water heater, but can't find the same size anywhere. the heater element is 3kw in a 0 shaped holder(as opposed to o shaped) fitted to the side of the boiler, fastened with 4 bolts, the stat is a 5" long cylinder shape. It's probably really old as its temps are 100-160 fahrenheit. I need to replace as i can hear it boiling at night.