Abstract: Safety mechanisms for a plumbing fixture supplying hot and cold water through a common line. One mechanism is mechanical and the other electrical. The mechanical mechanism makes use of a mechanical linkage between the hot-water valve and an auxiliary cold-water valve to flush residual hot water out of the common line with an excess of cold water. The electrical mechanism uses a microprocessor to activate the cold-water valve when the hot-water valve is shut of, this flushing the residual hot water out of the line with an excess of cold water.