A reducer normally refers to a fitting that is used to reduce the diameter of the suction piping to fit the pump intake. It is thus used to join two pipes of different sizes. Reducer is available in both eccentric and concentric designs. Concentric or eccentric reducers are used to properly reduce into and out of circulating pumps. The various advantages include keeping big pipes and small pipes together as well as reducing noise and vibration at the same time.

They are manufactured in a large number of materials, like Rubber, Stainless Steel, Carbon Steel, Copper, Nickel, Polypropylene, PVDF (sanitary control). Also known as "tapered expansion joint", the reducers made from rubber connect unequal size pipes that share a common centerline. These joints eliminate the need for metallic reducers and at the same time provide sound and vibration isolation and expansion compensation. The concentric reducer pipe fitting also allows both the inlet and outlet ends to align to a common center line.

Some of the important parameters used to select a concentric reducer are pressure/vacuum, max temp compression, approximate force, elongation etc. They are manufactured in various alloys, schedules, sizes and flange configurations. Concentric reducers frequently trap air when used at the suction of the pump.

Some of the industries where they find application are oil, gas, petrochemical, onshore and offshore sectors. They are used in both cargo transfers operations and vapor recovery systems. Reducers for vapor recovery include a pin on one flange and vapor hole on the opposite flange. Concentric reducer save installation space and reduce costs. Piping systems must be anchored when using concentric reducer.