You can probably get an RV water heater element at a big box store, too. But remember most home water heaters run on 240-VAC, so you need a 120-VAC element.
Suburban uses a 1440-Watt 120-VAC element. I think Atwood chose more line 1000-Watt. Doesn't heat as fast, but it conserves a little of your precious 30-Amp total from the campground pedestal and your main coach breaker. I put a 1000 in our Suburban and based on my test at home, I think I'm good with a little slower recovery to save 4-Amps of current draw.
You need a 1-1/2" Socket for Water Heater Elements, Home or RV. I used an old (VERY) heavy duty mechanic's socket and could barely get it onto the hex for the sheet metal around it. The cheap sheet metal socket slips in better. Element seals with an O-Ring and comes with a new one.
