Time for a new RO Membrane?

Discussion in 'Bulk Reef Supply' started by TheEngineer, Feb 7, 2018.

  1. TheEngineer

    TheEngineer Formerly icecool2 R2R Supporter Reef Squad R2R Excellence Award Showcase Editor Build Thread Contributor Delaware Reef Club

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    I can't recall the last time I swapped out my RO membrane (probably around 4 years ago). I've noticed my outgoing TDS has crept up from a typical 1-3ppm to 3-5ppm coming out of the RO stage. Is this my indication to change the membrane out?
     
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  2. Shores805

    Shores805 Rogue R2R Supporter

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    Few other variables needed. Your RO unit isn’t plumbed to your ATO right? What’s the TDS of your tap? What’s your rejection rate? Are you using quality cartridges/ when’s the last time you replaced them? Also if you’re relying on those inline TDS gauges they’re likely inaccurate.
     
  3. TheEngineer

    TheEngineer Formerly icecool2 R2R Supporter Reef Squad R2R Excellence Award Showcase Editor Build Thread Contributor Delaware Reef Club

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    Input TDS: ~150 (varies, but I'm on a well)
    Input pressure: 85 PSI
    Rejection rate @ 5ppm: 96.6% @ 1ppm: 99.3%

    I last replaced the pre-filters in 2016. I use an inline TDS meter, but verify with a handheld.

    This is not hooked into an ATO.
     
  4. Opus

    Opus Valuable Member

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    You are still within specs for the normal membrane so you are probably good. It all comes down to costs at this point. The higher your tds the faster you will use up your DI. At tds of 2, you will get around 2200 gallons out of your di. At 5 tds you are only looking at 890 gallons from your di.
     
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  5. Actuarious

    Actuarious Member Partner Member 2019

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    Is this assuming no CO2? So if I have 7TDS going in and my cartrage lasts about 150-200 gallons, is the rest due to CO2?
     
  6. TheEngineer

    TheEngineer Formerly icecool2 R2R Supporter Reef Squad R2R Excellence Award Showcase Editor Build Thread Contributor Delaware Reef Club

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    I have high CO2. I degas the water before going through DI
     
  7. bif24701

    bif24701 Valuable Member Build Thread Contributor

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    That is a good move on your part.

    I find that inline TDS sensors are more accurate than hand held simply because the water will quickly absorb anything it can from the air, container anywhere.

    I would replace it. 96% at 85 PSI isn’t good performance. Be sure to check the carbons blocks, if they allow any chlorine/ chloramines through to the RO membrane they will oxidize it thus degrading the filters performance.
     
  8. TheEngineer

    TheEngineer Formerly icecool2 R2R Supporter Reef Squad R2R Excellence Award Showcase Editor Build Thread Contributor Delaware Reef Club

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    No chlorine or chloramines in my well as of my last water test. I do think I’m overdue on replacing the pre filters.
     
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