Once a week I empty all 5 inside litter boxes into a super-duper heavy weight garbage bag, scraping everything off the bottoms. This goes in a special trash can outside. Then I line the litter boxes up outside on the patio and spray them thoroughly. Brush with an old dish brush, rinse thoroughly and dry with a towel. Refill and replace.

I also have 5 litter boxes outside in a specially-built shelter and a kids' old playhouse. They get scooped daily and a sprinkle of Arm & Hammer weekly. I clean them thoroughly about every other week. They get less use.

No one seems to be in a hurry to use them when I finish.