Dispenser mixing module and method of assembling and using same

A mixing module that includes a mixing chamber formed of a cold flow material and placed within a housing which includes a compression device for compressing the cold flow material through which extends a reciprocating rod, preferably in the form of a valve rod relative to one or more chemical ports formed in the mixing chamber to mix or deliver chemicals within a mixing reception recess. The mixing chamber features a locking arrangement between the cold flow material mixing chamber and the housing which acts to prevent movement of the mixing chamber within the housing due to a sticking of the reciprocating rod to the mixing chamber which otherwise produces a position change in the mixing chamber as the compression device is temporarily compressed until the rod becomes unstuck and releases. The mixing module also includes an open front and rear end housing with releasabele rear caps allowing easy insertion of the mixing chamber preferably having an annular front end rim as the locking member for receipt within a corresponding recess in the housing.