C4C and Pitlove made some good points, hope things are going well for you. I’ve had a lot of cats and luckily have never had any litter box issues. I buy a variety of litters and my cats use the box no matter what brand it’s filled with. Have had my share of UTI and crystal issues as well with my boys. I use totes as litter boxes now, too. Have been using them for years. In the past when I had many more cats than I have now (13 at one point), I also used kiddie swimming pools as litter boxes in my basement. The hard plastic ones. Good size, high enough to keep the litter in but not too high for older cats or kittens to climb in and out.
