Abstract: A dosing valve apparatus for introducing a metered dose of a second fluid to a first fluid comprises a first, or main body, portion (1), a second ball valve portion (3) and an end cap (2). The main body (1) and ball valve (3) contain first and second chambers (13, 14), respectively, into which flow the first and second fluids. An orifice jet (8) and needle valve (11) control flow of the second fluid from the second chamber (14) to the first chamber (13). Within the first chamber (13) is a pivotable paddle (7) which is adapted to act upon the needle valve (11). In this way, flow of the first fluid into the first chamber (13) acts upon the paddle (7), which in turn causes the needle valve to at least partially open the orifice (8) allowing the second fluid into the first chamber (13) to mix with the first fluid.