I have two rats, they both have those drinking bottles you attach to the side of the cage with a little metal tube at the bottom and a little metal ball inside the tube that controls the flow of water. Every now and then, probably about 3 times in the past year, I found the water wasn't coming out of the tube - I guess the little metal ball got stuck. Now I do a 5 second check every single morning on every water bottle by tapping the bottom of the metal tube to see if water comes out onto my finger - this morning it didn't, the ball was stuck. A good shake and it's working perfectly again. I tell you all this because I think it's sensible to do this daily check - it would be awful if your rat, hamster, guinea pig couldn't drink anything because it looked like they had loads of water but you didn't know they were actually going thirsty. So just letting you all know this can happen. Also, sensible to have two water bottles if you can, so there's always a back up.