>Has anyone cleaned their tanks succesfully?

I use something that goes under the trade name of Stericlean. It's used in
breweries and wineries as a cleaner and sterilizer on winemaking and brewing
equipment, which should be close to the hearts of Westfalia owners :>)

Anyways, it contains sodium hypochlorite, potassium bromide, potassium
permanganate, sodium phosphate and sodium lauryl sulphate (yum!).

It comes in powder form, mixes well with water and does a great job of
cleaning, sterilizing and just plain freshing up anything grungy. Put some
in your tank, add water, run the faucet/tap apparatus to draw the solution
into the system and let it sit over night. Then, go in the house and have a
beer. Drain and flush the system with fresh water in the morning.

Roy O.
'87 Westfalia (till death us do part)