i still cant get my head around your description mr bit, im lost all togeather.
pressure gauge should be here tomorrow. from vyair.
Its very straightforward , the attached pic should help. Ignore the fact its all compression joined and brass plumbed. Its just what I had lying around and my system at the time was fitted in my first floor flat so had to be completely fail safe and free from leaks.
The red needle valve to the right is my waste valve set to its optimum ratio for waste/pure.
Notice the bypass to the left and the ball lever, its open to flush the system. If I closed it a quarter of a turn it would start making pure.
Most 4040 ro's will just have a plastic ball lever style tap on the waste hose, in order to flush it you will have to fully open it and then partially close it again to make pure water. Problem is setting the tap back in the right place each time, some people mark the spot the tap needs to be set to.
A needle valve is more finely adjustable ( the tap with the red wheel in the pic ) and retains continuity because if you fit a bypass and second tap as I suggest you need never adjust it again.
If buying from vyair, just speak to Phil about it. I am sure he can supply you all fittings and explain it to you.