As long as he can pass urine without any problems you may be able to wait.
However if he cannot pass his urine, if he seems in pain, lethartgic or feverish then I'd see the vet today. Only you can see and judge how sick the dog is to determine if its see the vet now time or OK to wait.
This might be from bladder stones or crystals, urinary tract infection, or prostate problems.
Do try to keep him drinking and don't be upset with him if he makes a mistake in the house as he may not be able to help it.
Hope this helps you!
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