Question: Doesn't the water heater thermostat cycle only every five degrees? If so, that may be a problem since it wont turn off the heat soon enough to keep the eggs from getting too warm. I may be wrong on that, just asking. OR maybe there's another type that has less of a range. I can't remember-didn't you hatch some in your other bator already? Did it have that type of thermostat?
So many people have made their own bators with styrofoam coolers. We found one on the side of the road in perfect condition and DH was thinking about taking the guts out of my wooden MegaBator he made and putting them in it, but I wouldn't let him fool with success, LOL. Still, we may make one from styro ourselves some day.