The recirculating shower is simply to use as little water as possible, but still have more the a two minute shower. The run off from the shower is passed through a basic canister sponge filter(each user has there own sponge & disinfected in milton between uses). A small pump simply pushes the water flow back through the shower head. If you start off with 0.6 litre of water boiled from microwave and you add it to 1 litre of cold water, you can then prime the whole system with approx 1.5 litre of 40 deg c (approx) shower spray. After a days hiking in the hills, a spray down and a rub with a sponge using nice warm water...is a luxury....lol. You can stay under the shower till the water turns too cold, or you can have a jug of warmer water in the shower to 'top up' the heat. Not perfect....but beats carrying gallons of water for showering.