If you don't want to flush the toilet with the used shower water then you need either:
(1) A pressure pump and a momentary on switch/button to start the water pump from the fresh tank
or
(2) A 12v solenoid water valve and a momentary switch/button if your water system is permanently pressurised.
This is so you can do that sqirt of water before you turn the mix master on and another squirt as you see it sail away
then a final sqirt without the mix master running to put a water seal in the bottom of the bowl. The other mod that goes with this is to cut most of the rubber impeller blade off the secondary pump mounted behind the mix master chopper blades (you will see what I mean when you unbolt the pump). By cutting the rubber blades short the water can squirt through without the mix master motor running and it's heaps quieter. I cut the 90 deg outlet pipe in half and fitted the neck bit inside the larger collared bit the screw on to the pump and glued it in place with plumbers glue. It's hasn't been connected up yet so I'm not sure that was a winner or not, could be nasty if the end blowes out while the mix master is in action
We saw the Toilets go on special at Whitworths too and realised it was a Whitworth unit anyway so intialy we were a bit pee'd off but after further checking it wasn't the luxury fully enclosed ceramic bowl unit that was on special so we didn't feel so bad. The 12v solenoid valve is an expensive unit, we have it now and not sure that the secondary pump might have been a better idea, we won't really know till we see if we will have the main pump running full time or on a switch. Might even do the shower water flush and a squirt of fresh water after .... too many possibilities.
T1 Terry