As long as we're on the subject of water ...
Every year to two years, disinfect your freshwater tank with a bleach solution of one to two tablespoons regular bleach per gallon of water, filling the tank at least 3/4 full and drive around for 15 minutes or so, turning frequently with lots of stop and go to get the bleach solution sloshing all around inside the tank.
Then, run the the bleach solution through all your plumbing lines (galley sink, bathroom sink, shower, and head) for two minutes per line.
If you have a separate gray water tank, fill it at least 3/4 full of the bleach solution (it will be partially full due to flushing the plumbing lines) and drain the rest of the bleach into black water tank through the head. Drive around again as before to get bleach solution splashing around inside the gray/black water tanks.
Drain the bleach solution into an RV dump site and refill the freshwater tank with known-safe potable water and repeat the whole process to flush out the bleach, including completely draining the whole system again.
Finally, refill your fresh water tank again with known-safe potable water. At this point, your fresh water tank and plumbing should be mostly germ-free and the water safe to drink.
(Previously in this thread was a discussion on cleaning your black water tank versus just partially disinfecting as described here.)
Add 1-2 teaspoons of baking soda per gallon of water when refilling your fresh water tank to keep the water from going stale and tasting "off." The baking soda won't harm you (and will actually act as an antacid) but may affect some recipes that rely on acids such as vinegar or fruit juice.
Note: You must use regular chlorine bleach ... non-chlorine bleach will not work for disinfecting. The ingredient to look for on the label is sodium hypochlorite. Because you'll be flushing the system completely, it doesn't matter if the bleach contains added soaps, perfumes, and dyes.
Also, this bleach solution is much, much stronger than that used to disinfect drinking water ... well above EPA maximum safe levels for drinking water so be sure to flush your plumbing system completely.
Finally, be sure to use fresh bleach. Chlorine bleach had a finite shelf life, losing 20 to 50 percent of it's effectiveness in a year.
