I put a folded paper towel under Lily's wheel, which is usually where she pees. The PT soaks up most of the pee, and catches most of the poo, too. So I change the liners every three or four days, and put them in a laundry pile. Then when I have enough liners to make a small load (usually about six or seven liners, I have 12 altogether), then I do a wash.