Sometimes they associate the pain of going with the actual litter box which will bring about inappropriate peeing in the house. The carpet has to be cleaned with an enzyme cleaner designed to eliminate urine odor. If it's not, he'll keep being drawn to that area. Have you tried placing a different litter box close to the carpet where he's chosen to pee? That might encourage him to go there instead until this is over. I wouldn't discourage the sink peeing if this issue is going to be very short-termed. That's so easily disinfected and it won't damage your house.

You could also try putting some old towels or a blanket on to off some plastic and putting it on the carpet after cleaning it with enzyme cleaner. That works for our cat who has bouts of feline cystitis. She prefers soft things to pee on and instead of stressing her more out by trying to get her to use the litter box I just let her go on that and wash them.
As soon as she feels better she is back in the box.
Katharina

Thanks for the tips! My kitty is doing much better now. I did end up putting a litter box in the spot where he inappropriately urinated and he is being good and cooperating by going in the box instead of on the floor. Thank goodness! Also, I heard from a friend that mixing in a little water with his wet food is good to help hydrate him and that seems to be helping a lot as well.

Thanks for keeping us updated. It's good to read he's starting to feel better!! One of our members gave me this link about canned food when I thought I was having trouble with crystals in my cat. It was a great wealth of reliable information for me. It took me a long time to find a canned my cat would eat (and it's junk canned that she settled on) but the article said that even junk canned is better than dry food. I still leave dry food out as a back-up but my indoor cats primarily eat the wet as the main source of their diet. Here's the link below that you might want to read for further information.

Here is a link that might be useful: Cat Info. Org