cleaning water tank
Here is something I picked up while surfing:
Disinfecting Fresh Water Holding Tanks - Mike RVChem.net The following is the chlorine bleach to water ratio recommended by the US EPA for disinfecting fresh water holding tank systems: 'After the system is relatively clean, it can be disinfected. Six ounces (2/3 of a cup) of liquid chlorine bleach (Clorox, Purex, etc.) should be added for each 10 gallons of water the tank will hold. This makes a very strong (200 parts per million) disinfectant solution as suggested by the United States Environmental Protection Agency. By half-filling the tank, then adding the bleach and finally filling the tank to the top, a thorough mixture of chlorine and water is assured. Every water outlet in the vehicle should be individually opened to allow the chlorine solution to run through it until the chlorine smell is noticeable. This procedure is repeated at one-hour intervals until the chlorine smell is immediately noticeable.' (Credit; Everpure Water Co.)
As for the Black Streaks: Wal-Mart sells a product, I think it is called Black Streak Remover, that I found very helpful. Spray it on and wipe it off before you wash and wax your rig.
Enjoy the trip
John