I sanitize it every spring, and again if it sits over a month unused.
1. Use 1/4 cup of bleach per 15 gallons of tank capacity (I put the bleach in about 3 gallons of water to add it to the tank)
2. After putting in bleach, finish filling tank with fresh water
3. Drive around the block a few times to slosh bleach over all surfaces. Try to do a few hills and a few stop and gos
4. Run all faucets (both hot and cold lines), shower (both hot and cold), toilet, outside shower (both hot and cold) till you smell bleach. Don't forget that the water heater should NOT be bypassed for this as you want it sanitized too
5. Let it sit for 4 hours
6. Drain fresh water tank and water heater, fill with fresh water, rinse out all lines to get rid of the bleach. It may take another drain/fill/rinse to get out all of the bleach depending on how sensitive your nose is to the smell of the bleach.
Bobbo and Lin
2017 F-150 XLT 4x4 SuperCab w/Max Tow Package 3.5l EcoBoost V6
2017 Airstream Flying Cloud 23FB