RO membrane question about flow rates

[Shopco]

I hope this is the right place to post this; I did not see a forum for RO.

I am going to be using an RO membrane rated for 25 gpd (77° / 50 psi). After temperature correction the flow rate works out to 20 gpd @ 50psi but I will be running at 100 psi. The only pressure correction chart I found ( http://www.freedrinkingwater.com/faq.htm#MEMA) seems to indicate the pressure-corrected flow to be more than 40 gpd. I am wondering if anyone with actual experience thinks that sounds right.

The membrane is rated to 150 psi max and according to the manufacturer it will perform better at 100psi than 50 (fewer salts and better recovery rate).

Thanks

 

[ditttohead]

Yep, right forum to post in for this question.

The pressure compensation is fairly linear so a simple math equation will work close enough.

Membrane rating: 50 PSI @25 GPD @ 77 F, lets start by removing the temperature compensation out and work with only the pressure.

25 GPD / 50 PSI = .5 GPD per PSI.

.5 x 50 PSI = 25 GPD

.5 x 100 PSI = 50 GPD

There is more to it than that, but... no need to overthink it, this will be close enough. We have membranes that are technically rated for 20 PSI, we rerate them at 80 PSI and the same math applies and on the test bench, they are within 95% of the math shown above.

Temperature and TDS compensation are much more important factors to consider. I assume your water temperature is about 65-70 degrees? Dont forget TDS compensation. A guideline is to take off 1 PSI for every 100 TDS over the membranes test rating. This becomes very important on high tds water supplies.

Hope this helps.