A flow restrictor is a device with no moving parts which simply restricts the flow of water. All ultraviolet (UV) systems are designed to deliver a specific UV dose at a specific flow rate. Flow rates outside the design flow can be achieved in each model, however that will compromise the UV dose and a bacteria leak can possibly occur. A Flow restrictor should be used with UV systems to ensure that the water is exposed to the proper dosage of UV light, to properly sterilize the water. We offer flow restrictors in a wide variety of flow rates to match your UV system.