Series PRD/PRDM is a differential pressure regulator with a port for a downstream pressure sensing line. The sensing line feeds the pressure downstream of the equipment being protected to the top of the spring housing, which assists the spring in keeping the regulator open against the pressure directly at the regulator outlet. When pressure downstream begins to drop (as it would when a filter becomes more and more clogged), the regulator begins to close and becomes fully closed when the differential setting is reached. This assures against overpressure across the equipment. Molded and machined valves in 1/4″ through 3″ and metric pipe sizes in popular thermoplastic materials with a wide range of connection types. Differential set range 5-50 PSI.