I drain my hot water heater after every trip. When I get to our campsite and after the water is hooked up and on, I run the hot water for about 1 minute to help clean out whatever didn't drain out. Doing it this way I have never had a problem.
2011 jayco 33rlds, 2002 Ford excursion, v-10, 3:73 gears 4x4 mine. 2008 Suzuki sx-4, hers. Retired Air Force, now Retired.