Is there a DIY spray that deters cats from urinating in the house?

Is his or her litter box cleaned often enough? Have you ruled out any health reasons?

Seems like your cat has some litter box rebellion going on. Is your cat sharing the litter box with another cat?

Have you tried or changed the type of kitty litter lately?

There is something your cat does not like about it...unclean, type of litter, forced to share, size might be wrong, the scent of it, clumps, too hard to get to, out in the open or covered up,

You get to be a pet detective to solve this!

Best to you and your kitty.

If they go in the same place, sprinkle black pepper around the area. They like to sniff before going and the pepper distracts them. Also cleaning with Nature’s Miracle will get rid of urine and poo smells with an enzyme.

Don't forget the pad under the rug. The odor tends to soak in there, too. I had to replace sections of mine. Vinegar worked best for me for cleaning.

Cats generally don't go outside their litterbox which leads me to believe theres another problem. Have a Vet examine the cat to make sure there are no health issues. Cats don like change. Has there been any changes to speak of. Close entry to the room with the white carpet so no more accidents until you can figure out what the root of the problem is.