Welcome to the forum!
What brand of water heater do you have? Do you regularly flush it?
Depending on your brand, you may need to replace the anode drain plug and in any case should probably get one of these Water Heater Tank Rinser - Camco RV 11691 - Water Heaters - Camping World
so you can get the crud washed out of the bottom of your tank.
Rick, Nancy, Peanut & Lola our Westie Dogs & Bailey the Sheltie.
2007 Itasca Ellipse 40FD