This is Dr. Christian. Welcome to JustAnswer. Generally, urinating once a day isn't a problem, it just means his kidneys are functioning well. Kidneys that aren't functioning well produce so much urine that a dog will go numerous times a day. However, this does put a lot of stress on his kidneys and can be a sign of dehydration. If he is acting otherwise well (eating normal, active, etc.) then try putting some water on his food to increase his water intake. It is better for his kidneys that he not stay dehydrated as this puts stress on them. If you have more questions please let me know.
Sorry I probably didn't explain that well. Yes, it means that over time the kidney has to work harder than normal and can cause some problems such as early kidney failure at an older age or even cause urinary stones. That may take months to years but a constant of dehydration is not good for the body. It's not something that will cause problems for the kidneys over a few days.
My dog just vomitted a yellowish liquid out. Is this any cause for concern?
He is on interceptor.