I know this thread was posted ages ago but I just wanted to say that if anyone is searching for answers on why their cat is drinking a lot of water (which I did when I got a new cat), I wouldn't panic too much. My cat was new, and she's about 10 and I noticed she was drinking for around 5 minutes non-stop, at least 2-3 times a day, she's a bit on the skinny side and much prefers wet food to dry food. I searched what this could mean and I got really scared it could be diabetes or kidney disease. We took her to the vets who said she's fine, but to watch out for the amount of salt in her cat food, we changed her food (from Gourmet to Felix) and she stopped drinking such a large amount straight away.
I just wanted to post this in case you're worried about taking your cat to the vets, I know its unsettling for them.