I'm so sorry to hear that you're having peeing problems with your cat. My oldest cat also had the PU surgery and he's on Royal Canin Urinary S/O dry and wet food. He and Starr started peeing on my carpet in the dining room and entry way area. I put Storm on clomicalm for a while and it stopped his peeing but Starr was still peeing. Both cats were checked out and both were fine.

My vet recommended that I put more litterboxes out and to also start using cat attract litter. You can buy it at Petsmart or online and if it doesn't work then Petsmart will refund your money. I just added it on top of the old litter that I was using. It's worked wonders and now I don't have peeing problems any more. The litter also comes with a booklet that tells you what to do about cat spraying and peeing problems. I've also been using 2 feliway plugins and I use the spray before I go to bed at night.

I hope that something will work for you. I'd hate to hear that you had to rehome your beloved cat. Good luck.