Originally Posted by cpaharley2008
here is what you can use for you gray/black tanks. Fo r your fresh tank and more importantly your fresh water lines, a mix of 4 oz bleach to 2 gallons water, flush and repeat at least twice a year. Some bicarbonate soda in between will keep the fresh water fresh.
That's the approximate 'mix' I've used for at least 40yrs to sanitize RV water tanks. I usually add enough water (& chlorine bleach) to fill the tank(s) about a quarter full, then drive or tow for a half hour or so making sure to make several turns, stops, etc, so the water sloshes around in the tank. Afterwards I try to drain much of the water by running it through the lines/faucets to sanitize them also. Once in spring & again in fall
should do unless you get some questionable water & want to 'clean' the tank again to get rid of taste, odor, etc.