I hear you! I have had the same 10 cats for several years, but suddenly one of them has decided to start peeing in one of the rooms. I took her to the vet to rule out anything medical, and even though she is a huge cat, nothing seemed to be wrong. I thought maybe because she was so big, she was having trouble getting into the box - although it's just the pee she is having trouble with, the poop not being one, but she keeps on doing it. Litter boxes (4) scooped out at least 3x/day. I put down puppy pads on her "favorite" spots, but I'm getting awfully worn out by this. Can you suggest anything?
RESPONSE:
She is stressed or upset for some reason. You need to try and figure out what has changed that may be bothering her. The sand may be bothering her feet. Because she is big, she may feel the boxes are too small. She may not like the locations of the boxes and the competition for them. Only 4 boxes with 10 cats may no longer be enough. Get some Dr. Elsey's Cat Attract litter or Cat litter attract additive and see if that will encourage her back to the box. If you can, put a fresh litter box in her favorite spot and see if she will use it there.
Bottom line, you need to figure out what it is that is keeping her from the box and try and fix it. Try different things and see what, if anything makes a difference. Also, make sure you clean up the smell completely with an enzymatic cleaner made just for cat pee or she will keep wanting to go there.
In the meantime, put on your detective hat and start sleuthing!