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Old 09/16/2018, 06:53 PM   #1
FirstContact
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RODI: Second Membrane Failing Early

So this year I added a second membrane and booster pump to my RODI. The booster pump from BRS has worked great. The add on membrane kit not so much. Basically, I think the waste water from the first membrane fouls the second membrane very quickly and then you just wasted $45 on the membrane and throw more money away on DI resin. Okay. Booster pump has worked great though.

Iím only feeding my first membrane about 125 ppm TDS. The waste water output from the first membrane is 185 ppm TDS. A second membrane should be able to handle that right? My water pressure before the first membrane is 85 psi. No issues with the first membrane at all; so, it canít be a problem related to the prefilters or water quality. This is the second membrane I have tried as a dual stage with waste water feeding the second membrane from the first. It definitely just doesnít work for any reasonable amount of time. I put a new membrane in the second stage in April. It now runs at 35 ppm TDS with the flush valve open and 50 ppm with the flush valve closed. I always get several years out of my membranes except this dual stage set up where the waste water goes to the intake on the second membrane. Starts out great measuring at 2 or 4 ppm but that doesnít last and the membrane is quickly fouled. My first membrane puts out 4 ppm TDS. Based on advice from BRS, I tried reseating the second membrane. Nope, doesnít work. Swapping out the RO tubing making the second membrane the first and the first membrane the second doesnít work either. It runs 28 ppm TDS with the flush valve open. That just proves the membrane is fouled. My HM Digital TDS triple in line meter is new and installed correctly. Also have a Hanna hand held. So thereís really no way for the first membrane to continue to work great and the second membrane to fail so soon except for the fact that your feeding it highly concentrated waste water from the first membrane? Right?

BRS says this works for them long term and that their TDS from their second membrane runs about 7 ppm. I spoke with them Friday regarding troubleshooting. Iíd love for this to work, but I canít see trying this with a 3rd membrane unless someone can tell me what Iím doing wrong.

Anyone have any thoughts? Does this work for you? Whatís different about my set up? Does this not work for you also?


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Current Tank Info: 120g Reef 100g Rubbermaid Sump, 20g Refugium; previous tank: 46g Drilled; Self Plumbed, Birds Nest, Anchor, Xenia, Zoas, Yuma Yuma Ricordea, Chalice, Mushrooms, Brain, Acan, Anenome Plate; Clams, Other Inverts, Fish, Live Rock
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Old 09/17/2018, 04:29 PM   #2
outssider
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Quote:
Originally Posted by FirstContact View Post
your feeding it highly concentrated waste water from the first membrane? Right?
but 185 isn't high. A lot of people run one membrane with tds for the source water much higher than 185.....mine is around 250 and my membranes last for years.....

this is what I use...…

https://www.ebay.com/itm/Dow-Filmtec...gAAOSwU91afHes


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Old 09/17/2018, 08:58 PM   #3
FirstContact
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Yup, I’m using DOW Filmtech from Marine Depot, but 100 gpd.


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No man is an island entire of itself; any man's death diminishes me, because I am involved in mankind; never send to know for whom the bell tolls; it tolls for thee.
John Donne

Current Tank Info: 120g Reef 100g Rubbermaid Sump, 20g Refugium; previous tank: 46g Drilled; Self Plumbed, Birds Nest, Anchor, Xenia, Zoas, Yuma Yuma Ricordea, Chalice, Mushrooms, Brain, Acan, Anenome Plate; Clams, Other Inverts, Fish, Live Rock
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