A plumbing system operable to automatically introduce antifreeze into the hot and cold water systems responsive to a signal from a controller. In one embodiment, the optical system has optics configured to image the apertures of an optical input mask onto the pixels of the SLM and to form an optical spot array by imaging the light reflected by the pixels onto a plane orthogonal to the plane of the mask. In one embodiment the mixture includes from about 50 to about 80 volume percent dispersoid particles.