Ko te punaha tohanga wai he punaha nui o te whakamaarama ahumahi, ko te nuinga o te waahanga o te papu, te whakawhiti rere, te pukoro rere, te tirotiro i te pāmahana, te solenoid valve, te tātari, te evaporator me etahi atu waahanga. Ko te rere o te rere te take tino nui i roto i te punaha wai, a ko tana mahi ka pa tika ki te paanga whakamatao me te tere whakamahana.