valve cartridges 52 54 can be varied smoothly e g linearly between these two extremes this is brought about by meshing equally sized gears 58 60 with the same main gear 64 fig1 to 13 show a mixer tap 100 with another mixer valve 200 according to the present invention as shown in fig1 mixer valve 200 is arranged to be mounted above the work surface 42 within the main housing 106 108 of a mixer tap assembly 100 as before input supplies 14 16 are connected to the base 15 of the mixer valve 200 radially protruding levers 30 31 are turned to rotate gears in the same way as shown in fig5 to 9 as the mixer valve 200 is above the work surface in this embodiment there is no need for control sleeves to connect the levers 30 31 to the mix and flow control elements connection is more direct as shown in fig1 one difference in this embodiment is that the output from valve cartridge 50 is provided to a supply pipe 104 that extends out of the top of base 15 and is connected to the base of spout 102 other than this the internal mechanisms of the mixer valve 200 are the same as those illustrated in fig5 to 9 fig1 shows the presence of a mixing chamber 110 in use therefore the user operates one of the radially protruding levers 30 31 to control the flow rate of fluid ejected from the mixer valve 20 200 to be carried to the spout or other outlet of the assembly in which the mixer valve is mounted independently of the flow.