
hopefully you can see the pic,
this is how I have set up my 4040 ro on Phil's (vyair) advice,the valve on the right is the gate valve and is already set to the optimum waste to pure ratio and the valve on the left (bypass) is the gas tap, its open in the pic, so all the water is flushing to waste, if I turned it fully anticlockwise a1/4 of a turn or 90 degrees it would be closed and I would be producing approx. 50/50 waste/ pure.
Hope thats helped you out.
Simon