In order to prevent a liquid such as shampoo or water from being circulated from conduit 32 into air pump 50, the various openings on valve 26 and the various connections of valve 26 to conduits 32, 56, air pump 50, conduit 54 and conduits 30 and 36 are arranged so that the only positions available for discharging a fluid from valve 26 into conduit 18 are water shampoo mixtures, water or air, as i