I'm sure there are many good ways to do this, but here's what I do:

I leave the water in the tank when I get home from a trip.  Before leaving on the next trip, I add some chlorine bleach to the tank and run the faucet until the water comming out smells like bleach.  I wait a few minutes (or longer if I can) and then drain the system.  After that, I add some water, run the faucet, and drain again.  Then I fill the tank for the trip.  If there's any bleach left, it won't hurt, since its basically the same stuff used to chlorinate city water.

Bill
------------------------
 I drink my tank water all the time.  I also drain my tank after each camping trip and
 once a year I clean it with some cleaner/disinfectant junk.  I also have replaced the
 hoses that run from the tank to the sink, the hose I removed was BLACK inside.   Be
 sure to put plumber's anti freeze down the drain in winter or the freezing water will
 crack the  water trap.   M

 On 12 Jul 2002 at 12:01, John Brush wrote:

 > Soliciting advice from those in the know:
 >
 > What is considered the proper method of caring for the water tank in a
 > westy, or in my case, a pop-up camper? What I am looking for is what
 > people do with their drinking water tank between trips.