Line size for homemade RO setup

[GoldyCon]

I’m making a 2x400gpd ro system using an aquatech 8800 pump. The pump and feed ports in the filters are sized for 3/8 while the discharge ports are all sized 1/4 inch. Should I reduce everything after the pump (or pre filter?) to a standard 1/4 fitting? I don’t know why this tubing size is so confusing to me.

Also, where do you guys find these plastic fittings? My local hardware store doesn’t carry them so do I need to go to a special store or do the big box stores carry them?

[Keitha333]

I just built one this year as well. I would not restrict flow before the membrane that can be controlled after. To me it seems like you will get less flow across your membranes.

[gbeneke]

Ebay has the pumps and membranes but Amazon seems like the best source of fittings, look for 1/4 NPT thread to 3/8 Ro fittings. I would stay 3/8 in case you expand you unit with more membranes.

[ecolbeck]

On my RObucket the only lines that are 1/4” are the post membrane concentrate lines. This makes sense because the concentrate line is the only one that has restriction to build pressure in the system. All other lines should be 3/8” to maximize flow.