We have an 8yr old male doberman and a 5 month old female mini dachshund. The doberman has been house broken since he was 12 weeks old and never had any accidents in the house. Ever.

Few months ago we got the female mini dachshund puppy. She was 2 months old at the time, now 5 months old. Wife is still working on house training her.

The problem is that over the last couple of months, the 8yr old male doberman has started pissing all over the house. After 8yrs of never once doing it, it's about a twice/week occurrence now. It's not needing to go to the bathroom because he goes out regularly and half the time it's within even a few minutes of coming in. Also when he does it, it'll be several small spots instead of one big one....like he's marking his territory. He's been to the vet recently and checked out fine so I believe it's 100% behavioral.

What can I do to fix this?

Has the Doberman been fixed?

No. never had him fixed when he was younger due to an issue of being anemic. Vet said no surgery unless absolutely necessary because higher chance of complications than other dogs. And it's never been an issue before so never revisited the topic.

Elect-tro shock therapy!

Dog is marking territory sounds like. This might not be the right thing, but the next time I caught him Id put him in the kennel for 3 days. Only let him out to eat and bathroom on a leash. Then give him supervised out time for a few days then go back to normal. And repeat as necessary. He knows what he did to get put in the kennel, make him think about it.

Im no dog trainer, but I don't believe dogs have the ability to reason like that. They don't know if it was the piss they took or the cat chit they ate 2 minutes before, or that they jumped on the bed while you were at work. But to the OP is he marking spots where the little dogs pees? Are you actually catching him in the act? I'd imagine when the little one stops peeing in the house he will stop as well

I agree that dogs do not have the ability to reason, that's why it's important to catch him in the act. If you catch him in the act, reprimand immediately and he'll know exactly why. I don't see any other option. Kenneling him while in the house should prevent future occurrences but may not address the problem itself.

Agreed. Catch him and immediately nick him every single time. Turn up as needed.

I think dogs absolutely have the ability to reason. We put retrievers in situations where they have to make choices and figure out what they are suppose to do. The ability to make the correct decisions on a consistent basis is what separates the really good from the average ones.

Putting the dog in the kennel will not help a thing. He won't put 2 and 2 together in that manner. Put him on lead and do obedience work with him every day for a few weeks. That should help clear the air about who runs the show. I bet it will cure your problem.