FPPI® 1/2 in IPS brass union with orifice is specifically designed for use in the pressure sensing line for fire pump systems. The union is fitted with a 1/4 in orifice which will provide adequate pressure drop into the sensing line without allowing unnecessary pump starts due to major pressure fluctuations that may be indicated in the larger diameter 1/2 in-line. The union is only allowed to be used where the water is clear and will not allow sediment to block the 1/4 in hole. Check with pump manufacture for proper use.