View Full Version : GPD of RO/DI

01/07/2008, 06:26 PM
Hello all,
I've got a question agout RO/DI. Is the TFC membrane the only thing that regulates the GPD rating? If this is true, all you'd have to do is upgrade the TFC membrane to a higher rated membrane, right? I've got a Kent maxxima RO/DI 24 GPD and would like to raise my GPD to 50 or 75 GPD, is this possible. How? If not, why? Thanks in advance!

01/07/2008, 10:12 PM
The rejection rate of the membrane does give you the GPD. You can change it to a different membrane but if you do, the way I understand it is that, you also have to change out the flow restrictor.

I changed my 50 GPD to a 100 GPD and I did have to change the flow restrictor.

01/08/2008, 04:55 AM

01/08/2008, 08:21 AM
The rejection rate of the membrane has absolutely nothing to do with the GPD. They are two different issues.

The rejection rate is the removal efficiency of the membrane. This is usually 96 to 98% rejection rate or removal for most 25-75 GPD RO membranes.

The GPD is based on how the membrane is wound. More layers of membrane fabric equals higher GPD.

Yes, you can just install a new 75 GPD Dow Filmtec RO membrane and matched or adjustable flow restrictor and you now have a 96-98% efficient system capable of 75 GPD at 77 degrees F water temperature and 50 psi pressure. You will more than triple your production rate since the Kent is rated at 24 GPD at 60 or 65 psi while the Dow will produce 75 GPD at 50 psi and 90 to 100 GPD at 60-65 psi.

01/08/2008, 10:21 PM
AZDesertRat, thanks for clearing that up about the rejection rate. I was only posting it the way it was explained to me. I do know it worked for me by changing the membrane and the flow restictor.

01/09/2008, 04:55 AM
Thank you, sir! I really appreciate the info! Thanks to you as well, strayvoltage!