This by-pass control relief valve is used in commercial, residential and industrial applications to regulate liquid pressure as supplied by a positive pressure pump. It is a diaphragm-operated type valve that protects equipment by opening at the desired setting to allow excess volume to be by-passed back to the source. It consists of a bronze body construction with NPT threaded male inlet and NPT threaded female outlet, sensitive rubber diaphragm, Teflon disc, spring and adjustment handle, and a tee handle.