View Full Version : RO/DI 100GPH convert to 75GPH?

11/17/2009, 06:22 PM
My current 100GPH RO/DI has 1:1.25 - 1:5 ratio.

Will my ratio change if I convert the membrane and restrictor to a 75GPH?

Buckeye Hydro
11/18/2009, 05:25 AM
100 gpd, rather than 100 gph, right?

If you use any membrane with a proper restrictor you'll get about 4 parts waste to 1 part purified water.


11/19/2009, 09:20 AM
Are you using an adjustable flow restrictor now or is it the wrong size as the rate should be 4:1? With the proper restrictor for all membranes the standard flow rate should be 4:1
You could achive the 1.25 to 1.50 with dual 75 GPD's if your pressure 65 psi or higher.


11/20/2009, 12:28 AM
I just put placed 2 empty 5 gal buckets. After running my system I got 1 bucket with purified and about 1.5 bucket of waste.

The system I have is fully automatic from puratek.

When the water level has been reached the float switch shuts down the output and then the unit flushes its membrane for 15sec. Then it goes on standby untill the water level drops again. It does this all day as the water evaportes.

The pressure out of my booster pump to the 100gpd membrane shows about 120-125PSI when producing purified water. The restrictor on my waste says "450"

I would like a higher rejection rate so my DI Resin last longer but I dont want to loose the efficientcy of the unit by going 75gpd.

Does my rambling help out at all?

11/20/2009, 07:59 AM
OK your answers make things perfectly clear and you answered the question about what they are doing to get the reduced rejection rate with the 450 flow restrictor as opposed to the normal 800. Without the details nothing makes sense as a 100 GPD should not achive those results.

Now with duel 75 GPD membranes and a booster pump with a flush timer you would achive far better rejection rates (98%) and have a system that produces more water (180+ GPD) and performs the same or better with rejection at 1.25:1.

To answer your original question I am unsure how a single 75 GPD membrane would perform in your system under tight restriction to get the low waste ratio. I have a feeling there is a reason they chose to build with a GE 100 GPD membrane as Filmtec's are the superior membrane.


11/20/2009, 04:14 PM
I guess I should leave it alone then. If it aint broken then it dont need fixing!

I will be placing my usual order with you guys soon. DI resin and filters.

Thanks for being there for us reefers.

11/20/2009, 06:53 PM
As they market more of these systems I am getting more calls to trouble shoot issues they can't answer. All the details are starting to fall together such as the 450 restrictor. You paid a lot of money for what you have I would go with it for now. I can say it makes our dual membrane Ocean Reef Miser system a real out performer.