I have a single post 4x40 rig. I use my recirc valve mainly to set the membrane pressure. The original valve (i call it the main valve) basically becomes a concentrate bleed-off metering valve, which I use to set the concentrate flow rate. With my single post running at 225 psi (controlled mostly with the recirc valve), I set my concentrate flow to about 30 gph. Then re-adjust the recirc valve to re-establish 225 psi. I'm usually done adjusting right there, but it occasionally takes one more iteration, as there is a small amount of interplay between the two valves. On my unit at a membrane pressure of 225 psi , when i set the concentrate flow rate to 30 gph, the percentage is a steady 6-7%, which works great for me. I have no flow meter on the recirc line and my approach seems to work fine, 3 years running.
The concentration doesn't keep climbing higher and higher because you are always bleeding off some concentrate. Just like a continuous flow evaporator. Once you establish the gradient, you're all set. On an evap it can take a couple hours to get the gradient. On an RO, it is a few minutes.
Last edited by jrgagne99; 04-27-2021 at 08:12 AM.
Boulder Trail Sugaring
150 Taps on Vacuum
Homemade 20"x40" Hybrid Pan - 15 gph
Homemade Steamaway - 10 gph
Waterguys single-post RO