need advice on RO/DI unit 100gpd

[phish guy]

so my boss wants me to find a good RO/DI unit, around 100gpd, for the store. i figured, who better to ask.

so . . .

-Which one are you using/have used?

-How much was it?

-How much water does it take make 1 RO gallon?

-About how long do the cartridges last/cost?


Thanks everyone.

[hellssephiroth]

a lot of that depends on the brand. i just bought the 7 stage RODI from bulkreefsupply and it is awesome. seems to me someone once told me not to go over 75 gpd because the membranes dont work as well? someone here plz correct me if im wrong

[MrRyanT]

I would recommend sending a pm to AZDesertRat or maybe he will post here. It seems to me that he is very knowledgeable about RODI systems.

[connecticut cichlids]

I was also looking at the brs 7 stage unit last week. I went back today to purchase it, and it was no longer offered on there web site! What a shame!

[AZDesertRat]

The average RO/DI system makes 75 GPD in a 24 hour period and wastes about 300 gallons to do so or a 4:1 waste ratio. You will want to stay away from most 100 GPD systems if they use a Dow Filmtec 10 GPD membrane as they are not really a RO membrane but are actually a nano filter which is much less efficient and will eat DI resin.
The 100 GPD GE Water (Osmonics) membrane is almost identical to the 75 GPD Dow Filmtec which seems to be the inductry standard. It makes 100 GPD at 65 psi and 75 GPD at 50 psi just like a Dow Filmtec.

Don't get wrapped up in "Stages", it means little. What the stages contain are the important point. For a good RO you need 3 stages and a good RO/DI you need 4, no more no less. You can make DI last longer by adding a second DI stage but things like dual carbons or the little dinky horizontal dual DI tubes are a waste of money and work no better or last no longer than a good single one.

You can get into a very good RO/DI for $169 and the absolute very best in the business for about $315.