Add a half-cup of bleach to every 15 gallons of water in the tank every month. Let the bleach mixture stay in the tank overnight, then flush out the tank and replace the water. The water in the tank should now stay fresh for one month.
Attach a water filter between the tap and the hose. You'll find these attachments at camping and RV supply stores. Fill the tank with water run through the filter as it removes particles and bacteria, which can spoil or decay the water.
Add eight to 10 drops of chlorine bleach into the full tank of water. The trace amounts of bleach will not harm you when you drink it or use it to wash in but will help to keep the water fresh and reduce bacteria. Drive around the block a few times after adding the bleach to slosh the water around and thoroughly mix the solution.
