Zero Odor is not cheap. but it's a lot cheaper than a vet, and presents no danger at all to the cat. Plus it helps your house immediately.
I have a neutered male, 12 years old, who did that his entire life until I sprayed his favorite surfaces with a product called Feliway. It's available in most pet stores. It's a pheromone that supposedly "calms" cats so that they aren't so agitated to have to mark their territory.
If he's puddling, this might help with that as well.
Someone mentioned bladder crystals. Have your vet do a urine test and make sure he doesn't have crystals. They are common in older cats and dogs, and, if he has them, changing his food could have a dramatic effect.
Is it found in pet stores????