What breed of dog is this?
Is he neutered?
Is he urine marking (small spritz on furniture) or urinating full stream?
Thank you for that information. When an older well trained dog suddenly starts going in the home it is usually due to a health issue. It could be a urinary tract infection or in looking up the breed I see that they are prone to a couple of kidney problems which should be checked out. Amyloidosis is just one. http://www.petplace.com/dogs/renal-kidney-amyloidosis-in-dogs/page1.aspx and developmental kidney disease is another.
Other factors could be bladder stones. I would bring in a urine sample for testing. This can at least rule out some problems.
Well, if you really suspect a behavior problem, which would be rare in an older neutered dog unless there have been changes in the home such as a new pet, baby, etc. then it will mean going back to the basics of house training. Until this can begin you may want to consider putting him in a crate when he can't be watched or keeping him in a room that can be cleaned up easily. It also means wiping out any trace of his odor with a cleaner made just for dog urine such as Natures Miracle. Start placing bits of his kibble in those areas so he learns it is an eating place not a peeing place. Most dogs do not like to eliminate where they eat and sleep.
I would also again take a look at the health, maybe another opinion from a different vet or maybe blood work needs to be done to make sure the kidneys are functioning correctly .