They don't really, though. If you try to collapse a kiddie pool it will be permanently damaged due to the stresses on the plastic. They usually ship in a box

They don't really, though. If you try to collapse a kiddie pool it will be permanently damaged due to the stresses on the plastic. They usually ship in a box the same size as the uncollapsed pool. The holding tanks come in all sizes - you can get them the same diameter and depth as a kiddie pool, just obviously thicker and heavier since they're actually designed to hold the weight of water without deforming.