I have a bad habit of not finishing the bottled water I drink, and they can accumulate so I sometimes end up with 10-20 half empty bottles of water. I hate to waste, so I will usually pour all the bottles into one and save it to make coffee since I figured the boiling water will make it safe to drink if it has been sitting out a bit. Occasionally the water will sit in my cabinet for a month or two before I get to using it, but always with a cap on.

In the last few weeks, my cups have started tasting very strange, but only after taking a few sips which start off great, then quickly start tasting like dirt or vegetal. It seems to happen whether I use fresh bottled water or the older ones, but is more noticeable with the older water. Is this the result of stale water or is there some other variable at play?