Sophie, the new arrival, drinks plenty of water. Yet... she never pees. I mean the only time I have seen this dog pee in two days is all over me when she was scared. She seems perfectly healthy but she really never pees.
If she's small and ever out of your sight, she may be doing it when you're not looking. With small dogs, accidents are sometimes very hard to see. Unless you catch it right away, you ma never notice that she's pottied especially on the carpet.
