Terry, I'm betting you have a Suburban water heater. If you read in owner's manual, Suburban recommends draining the water heater whenever it's not being used. Suburban uses an anode rod that reacts with sulfur in the water to produce hydrogen sulfide (sewer gas) and it's hard to get that stink out. I've gotten in the practice of draining my water heater after every weekend's use to avoid that problem and make the anodes last much longer. I even use a siphon hose to get that last 1/2 gallon off the bottom of the tank - that way, no water comes in contact with the rod between outings.
Don Ford
2004 Safari Trek 31SBD (F53/V10 20,500GVW)
'09 HHR 2LT or '97 Aerostar MiniVan (Remco driveshaft disconnect) for Towed vehicles
BlueOx Aventa II Towbar - ReadyBrake Inertia Brake System