afterfill tube depends largely on the local fresh water pressure this flow rate continues during the raising stroke of the float thus more or less water is delivered to the toilet bowl depending on the supply pressure and no mechanisms are provided for the adjustment thereof for these reasons it is devised herein to install an aftermarket flow splitting system 10 comprising a tee fitting 11 defined by two spaced fitting ends 11a and 11b and orthogonal end 11c a plastic clip on holder 40 suspends the fitting from one edge of the tank t each of the fitting ends may be shaped or formed for convenient connection e g in the manner of a barbed male shape which is conveniently insertable into tubing such as the afterfill tube at the tubular legs of the tee fitting 11 terminating in ends 11a and 11b and designated herein as tube segments 21 and 31 respectively are each provided with a manually operable valve assembly 22 and 32 each valve assembly in turn includes a lever handle 22a and 32a for manual adjustment thus the linear portion of fitting 11 takes the general form of a gang valve comprising two valves 22 and 32 the end 11b of the fitting may then be inserted into a tubing segment 35 provided with a clip 36 engageable to any structure of the ballcock or standpipe for directing a part of the stream therethrough end 11c may then.