For the last 3 months I've been suffering with chronic diarrheah. It was unpleasant. I couldn't figure out what was causing it. I tried changing my diet, habits, and nothing helped.
Finally I decided to clean out my cleaning-water storage bottle. See, I keep my cleaning water in a 1-gal (too small; I need to get a larger one) bottle under my sink, with a 1/8" hose that goes up to a standard spray-bottle sprayer handle. That's how I wash stuff in my sink. I also have a funnel and a tube going down to the bottle, so I can refill it without having to climb around under there to remove it and rethread the hose and checkvalve, etc.
Well it was disgusting. The submerged part of the fill hose was black with bacteria, and the bottom of it had a quarter-inch layer of dust and sediment and who-knows-what. So I dismantled it, cleaned it out, put in fresh water, and put a couple drops of bleach in there just in case.
And, after a few days, finally, my stomach is back to normal again.
I had been poisoning myself with some kind of bacteria. I didn't think it mattered much since I just used the water to spray things to clean it, and never used it for drinking or cooking (I have a separate 5-gal Arrhowhead bottle for that), but I guess the residue of this on my dishes, bowls, and pots and pans, was enough to botch my intestines in a big way.
Glad that's done with!