> How long is it safe for a dog to not wee.
Well for what it's worth, my girl absolutely refuses to 'go' anywhere off our property. The first time we were away overnight, having left by around 8 am when she did both before getting in the car, I spent pretty much all evening taking her out, walking her, from the hotel. The girls on reception were highly amused. What did she do - nothing. In the end I gave up and crated her for the night. I wasn't worried about the poohing as she'd not eaten much since the previous breakfast.
The next morning, again nothing, so we set off, and stopped in a service area where, finally, she peed. That was at about 11 am. So she'd gone from 8 am the morning before, to then. I was quite honestly, about to find a vet to catheterise her. She does hold, normally, for a long time comparatively but that was just too long! The next overnight trip, she did pee during the evening.
As for the refusal to empty other than in the back garden - heaven knows what happens if we move!! Early days, I tried taking her out front first thing when she always empties out back. I walked her up and down - nothing.