I have always used bleach thru my tank, lines and faucets but felt better to use bottled water for drinking and cooking.
My previous two RV's were truck campers . Where did i find more crud ? While cleaning the exterior of the RV or cleaning inside the water tank ?
Most TC's have water tanks inside the unit tucked underneath the cabover step.
Some truck camper owners cut a 6-8" hole in the top of the water tank , then sealed it closed using a marine deck plate which gets unscrewed in order to gain inside access to wipe the tank clean.
The stuff i found inside my tank really opened my eyes. :E
I'm glad i used bottled water and not the 'sanitized' water that wasn't. :)