grrr -- since the cat was peeing on the carpet, I decided that was a good sign the box was too dirty (which it was). So I decided to dump the box and spray it out, then let it soak in bleach water for a bit.
For a while now, I've been using the bottom of a hooded box sitting inside a big storage container -- the nesting was to help keep cat pee from going over the edge. Since I had everything disassembled, I decided to just get rid of the smaller box and just use the bin. So I hosed it out and left it sitting on the driveway on the side of our house to dry out.
Fast-forward a few hours and I'm backing out of the garage to go somewhere. CRRRUUUNNNCCCCCHHHH! Yep -- I had hit the darn bin. Best guess is that it blew from where I left it into the main driveway. Counting my blessings that's all it was. This cracked the bin on one end.
I had already been pondering cutting an opening into the side of the bin to make it easier for the cats to get in and out. I had pondered the possibility that having to jump in and out was making it less appealing for my old kitties. Since it was now cracked on the end, I elected to cut the opening out of the end instead. This hole starts about 6-7 inches from the bottom and extends to the top.
So, I get the box all set up with it's handy-dandy opening and go on about my business. A while later, I notice that the laundry room floor was wet. Wet, but not an entire puddle. So - you guessed it -- the cat managed to pee through the opening in the end.

I don't know if the concept is sound, but just needs to be refined to have the bottom of the hole a bit higher. Or if it would be better on the side of the box -- they tend to do all their peeing at one end - the end with the hole. I'm afraid if I just turn the box around, they'll still pee at the end with the opening and then be getting the other stuff in the laundry room that's behind the litter box.