An inflatable spa (100) is disclosed comprising a water cavity (112). The inflatable spa (100) further comprises a control system (200) having an air pump (232), a first check valve (260), positioned in an air passageway (230), and a drain valve (280). The first check valve (280) closes when the air pump (232) is stopped to prevent a backflow of water from the water cavity (112) to the air pump and opens under pressure from the air pump. The drain valve (200) opens when the air pump (232) is stopped to drain any water from the air passageway (230) and closes under air pressure from the air pump.
