RO plumbing for dummies please

[Paperman]

I's in the midst of gathering parts for a single 4" RO. Procon pump with centrifugal feed pump. Never seen one, never used one. I plan to add gauges where its obvious and know I need a couple flow meters. When reading I start to get confused when I hear of a recirc line back to the inlet of the feed pump. Also do I plumb for recirculating the soap wash water through for a while or is it a single pass and dump deal? Been searching for a line drawing but cant find one. Help a poor sap out, only a few months till the snow melts.

[madmapler]

Do a search for teuchtar. He is an engineer that designed a comprehensive set of plans for one like you're building. Click on his homemade RO thread and study it. All the info you need is in that thread including his plans.

[Paperman]

Thanks for the PM's and reply. Im on a good path I think. I was just wrapping my head around why feed back into the suction of the pump and not to the feed tank.

[maple flats]

To get a full explanation go to the reference above. The simple answer is that when you wash, after you rinse the sugar from the membrane Usually 5 minutes), you add hot water (typically 115 degrees) and soap. Then you start the pump, with both the permeate discharge AND the concentrate discharge routed back into the wash tank (10 minutes). Then you set the concentrate to drain (waste) and the permeate can either go back to permeate or to drain (waste). When the wash tank is empty, do a cold permeate rinse for 5 minutes. Change your pre-filter and put the RO to bed.
These times are from my owner's manual, but I typically go about 10-20% longer in each phase.