Siejuban Posted July 25, 2013 Share Posted July 25, 2013 I have been searching here to find more information about the size of the Flow Restrictor, but still a little not clear about it.... I have damaged my flow restrictor in my RO filter which is 40 gpd when I installing the flush kit, so I order replacement, they have choice of flow restrictor for 35 gpd membrane and 60 gpd membrane, I order both just in case. Which one is good for a 40 GPD RO system? If I use the 60 GPD, do I need to cut the length? Quote Link to comment
AZDesertRat Posted July 25, 2013 Share Posted July 25, 2013 I have not heard of a 40 GPD RO membrane but I would assume it could be a 25 GPD Dow Filmtec which is rated at 25 GPD at 50 psi, and 40 GPD at around 65 psi. I would use the 35 GPD capillary tube and trim it for between 3:1 and 4:1 waste ratio depending on if you use softened water and what your tap TDS is. If you have soft water and lower than normal TDS you can go 3:1 or even 2:1 if you understand the drawbacks and requirements or stay with the 3:1 to 4:1 if you do not have soft water and low TDS. Water hardness and TDS play a big part in how long a RO membrane will last and how well it works so it is important they stay well flushed via the waste ratio. Too little waste and you quickly foul a membrane and too much waste and you rob the membrane of pressure lowering your rejection rate or removal efficiency and shortening your DI life. You need to reach that happy medium for best performance and filter life. Quote Link to comment
Siejuban Posted July 25, 2013 Author Share Posted July 25, 2013 Mine is SpectraPure® Maxpure 40 GPD RO System, still on sale in MarineDepot. That is what I need to be confirmed, so, I think I will use the 35 GPD, just trim it to the 4:1 ratio then. Right now, I am using a spare flow restrictor which giving 6:1 before I got my order. My tap water TDS is around 50, not sure if it is soft. Thanks! Quote Link to comment
AZDesertRat Posted July 25, 2013 Share Posted July 25, 2013 Wow that is great tap water TDS, the average is around 250 today. Spectrapure calls for the red colored restrictor for the 40 GPD membrane as found here: http://spectrapure.com/AQUARIUM/MEMBRANES-FLOW-RESTRICTORS/Std-Flow-Restrictors/Standard-40-GPD-Flow-Restrictor Quote Link to comment
Siejuban Posted July 26, 2013 Author Share Posted July 26, 2013 Thank for the link, I should check that before I place my order. Quote Link to comment
Ismael Posted January 25, 2022 Share Posted January 25, 2022 Hello, what size of flow restrictor do I need for my 75gpd ro system? When I bought it came with a 300 restrictor, but according to what I read, I think it is very small, my water TDS is between 127 and 130, thanks. Quote Link to comment
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