When it comes to RV maintenance, your water heater should be at the top of your list. Most RV water heater tanks are made of steel—and that’s where the problem starts. The water you’re using at RV parks and campgrounds often contains hard water . That means it’s loaded with minerals like calcium, magnesium, limestone, and even iron. Over time, those minerals don’t just sit there… they attack your tank from the inside out . They cause: Rust and corrosion in the tank walls Sedi