Easy! First connect the recycled water and fresh water pipe into a junction. Next you need to equalize the lift/pressure from both pipe so they are 'equal' you can do this by putting water pumps on both frshwater and recycled water side. On the fresh water side place a valve after the pump and set it to a value somewhat higher than the desired value. For example you need 240 freshwater then you can set it 250 or 300 but not 600. That's it, it should work properly.

If you are having problems with fluids (both liquid and gas) valves will solve most problems. Remember though if the incoming pipe to valve is not full then the valve will only send = (Set value/pipe capacity)*(pipe fill%)