replacing a ro membrane

[dmirza]

I have a 75gpd reverse osmosis membrane on my water filtration system. I want to downgrade it to a 35 gpd membrane. Would I need to also replace the flow restrictor to do this?

 

[dmirza]

anybody have input on this?

 

[AZDesertRat]

Why would you downgrade? It will take over twice as long to make the same amount of water, the efficiency is still 96-98% either way and the same 4:1 waste ratio will still apply. That makes no sense?

 

[dmirza]

I read on the Reef Central FAQ about ro/di that anything larger than 35gpd is just multiple membranes glued together and results in less pure water. Is that information wrong?

 

[Reefjunkee]

You will still get the same rejection rate with either.Do You have a tds meter.I have a 100gpd and my tds is 54 going in and 0 coming out.And that is on 6 month old filters and 1+ year old membrane.I would just keep what I had if I were You.Like AZDesert said it`ll just take longer to make it with the same results.

 

[Reefjunkee]

Oh and if You were to look at the 35gpd it will have multiple layers also,just not as many.

 

[d4a2n0k]

Yes, very wrong. Maybe some of the cheaper membranes are like that.

Get a good brand membrane such as a Dow Filmtec 75 GPD and start making water without worry.

 

[dmirza]

thanks for the advice gus.

 

[AZDesertRat]

Stick with a 75 GPD Dow Filmtec, its still rated at 98% rejection just like a 25,35, 50 or 60 is. When you step up to a 100 GPD you sometimes lose efficiency as some vendors use nano filters rated at 90% rejection instead of reverse osmosis rated at 96 to 98%. Vendors who claim over 100 GPD at 98% for the most part are full of bull as no manufacturer who is ANSI/NSF certified has a membrane capable of over 100 GPD with one notable exception but thay are having trouble with the supplier and have pulled them from the market until they can supply their demand.

 

[dmirza]

I just found out that I have a 100 GPD unit, and I would like to downgrade it to a 75 GPD for the reasons mentioned above. Would it be ok to use an 850 ml/mn flow restrictor on a 75GPD Filmtec unit? I believe that they should be run with 750 ml. What would be the impact of doing this?

Thanks for the help.

 

[AZDesertRat]

You should be fine. The 850 will waste a little over 4:1 but not significantly.