In the application of either concentric or eccentric reducers, careful consideration needs to be given to the potential thrust developed toward the small end of the reducer, particularly when the piece is made as a reducing adapter involving a plain end or unrestrained joint of any kind.

Thrust restraint is seldom needed if grouted bell and spigot joints are used leading away from the small end. See Section Fourteen of the Price Brothers Concrete Pressure Pipe Engineering Manual for more details on restraining reducers.

Typical concentric reducer