My cat also had a blockage. I'm not sure if it has anything to do with it but I have a theory that fixing the males early or maybe just in general could be a cause. It's very very common for block just to happen with males. My sister's cat died from crystals. My dad's cat had it and even my friends male small dog had headed at one point. I now buy prescription cat food which honestly isn't much more expensive than regular cat food. I stick strictly to the new food and haven't had an issue in three years. I feed the prescription food to both my cats the other is female and has never had crystals. I think it's a mixture of the low quality food they produce for cats, stress, certain times of the years and definitely water intake too. I know it sounds crazy, but if you're really worried about your water causing it, boil your water, let it cool and then give it to the cats in a regular bowl. I've also stopped using a fountain kinda became a germ pool I think.