Hi, I'm Dr. Jill. I'd by happy to help with your questions.
Based upon your description, you're probably dealing with either a medical condition with one of the dogs causing them to urinate more frequently, or you're dealing with a behavior issue. You sound quite convinced it's the younger of the two, though you could separate them after they go out in the morning to make sure. The first step I would then recommend is having your veterinarian perform a urinalysis (testing a urine sample) of the dog that is urinating to see if there are signs of a medical condition such as a urinary tract infection, crystals in the urine causing irritation, or kidney issues. Bloodwork can also help look at kidney function and identify other issues that can cause increased drinking and urination.
If that all checks out as normal, then that points more toward a behavioral issue. At 1 year old, the puppy is probably starting to develop more adult behaviors such as territorial marking, and they may be both trying to do this in competition. Neutering would be my next suggestion if a medical issue is not identified as neutering can greatly curtail certain behavioral and territorial issues. And until a solution is found, not leaving either dog alone would be useful for preventing accidents. This can include having them on leashes with you at all times in the house, crate confinement when you are upstairs, or leaving them outside when you are unable to be with them. If you keep the dogs with you and see one in the act, you can redirect him outside. (If he’s not caught in the act, he will not identify any punishment or other cues with the urination. So punishment after the fact is ineffective and usually just causes frustration and anxiety with the dog potentially worsening the problem.) But before looking at training or behavior modification, I believe it is important to rule out medical issues to be fair to the pet.
I hope this addresses your questions and gives you a plan of action. If you have any further questions regarding this issue please don’t hesitate to ask…I would be happy to continue the conversation.
Thank you for the additional information! I would agree that a behavioral issue (such as territorial marking) is more likely to be the cause, though I would still suggest a urinalysis at your vet’s just to make sure we’re not missing something obvious (like crystals or infection). The next steps if that is normal that I would recommend are neutering and not leaving them unattended in the house in the morning. Again, if you can’t catch them in the act, you can’t effectively correct the behavior with training.
I’m not sure what cleaners are available in your area, but generally enzymatic cleansers are most effective for eliminating urine smells (enzymes help break down the proteins in the urine and help eliminate smell). Your local pet store staff would likely be able to give you recommendations on what works with their clientele. Amazon also has a variety of options.
Please let me know if there’s anything further I can address to be of assistance. Thanks!