Rendezvous Spa Specialties Foam Out is a defoamer that rids spa of foam caused by a concentration of body oils and other materials. This product also prevents and eliminates foam and froth caused by a variety of things. It is made of a fast acting, concentrated solution. Foam Out can also be used in therapeutic pools, fountains, and swimming pools. It is compatible with chlorine, bromine, ozone and mineral purification systems.