How bad is my water?

Discussion in 'Water Chemistry' started by mdbostwick, Nov 20, 2014.

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  1. AZDesertRat

    AZDesertRat Giant Squid

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    If your RO membrane is fuctioning properly the RO only TDS should be 96-99% lower than the tap TDS.
    So, with your 585 going in you should see something like 5 to 23 at the highest froom the RO. Using my system as an example my softened tap TDS is 560-600 and the RO only is between 2 and 3 using a Spectrapure 99% guaranteed rejection rate Select series RO membrane. When I was using an off the shelf 75 GPD Dow Filmtec membrane the TDS was between 13 and 15. The biggest advantage with the better membrane is now my DI lasts 5-6 times or more longer so the membrane paid for itself in the first year in DI replacement savings alone.

    If you know your tap water pH and alkalinity you can calculate the CO2 content of your water which may be contributing to your short DI life but check your RO TDS first.
     
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  3. Pdxile

    Pdxile Coral Banded Shrimp

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    How many gallons of water can you get out of a full DI cartridge? My well water is so "airy" that it comes out of the tap almost white and gasses off. Tastes great, through. Confession: I don't run DI anymore, I can't afford to blow through resin every 75 gallons. (After membrane I am 2ppm) On the spectrapure website there is an instruction sheet on creating a de-gassing device. I'd use one if I had the room for it. You might test your water for Co2 and see if that is your issue.
     
  4. mdbostwick

    mdbostwick Vlamingii Tang

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    Ok, so I checked my tds going in and it is at 600. after RO only it comes out at 14. which is still better than with the DI but not by much. Do you think I need a new membrane? I have had the same membrane since i bought it about 2 years ago, but it has only been used about the last year, maybe a little longer. If i need/should replace the membrane, I am hoping to be able to put a spectrepure membrane in it but it is not a spectrepure unit, so I would need to know how i can tell if i can use one or not.
     
  5. DSC reef

    DSC reef Giant Squid

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    As long as the membrane matches your gpd you pretty much can use any make of membranes. I have a coralife 50 gpd unit but I changed all filters and resin to Aqua fx. I'm getting a new aqua fx membrane next week. Just make sure your new membrane matches your gpd on your unit.
     
  6. mdbostwick

    mdbostwick Vlamingii Tang

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    I thought the membrane was what distinguished the GPD on a unit. Shows how much i really know about RO/DI units.:confused:
     
  7. Vinnyboombatz

    Vinnyboombatz Giant Squid

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    It does.You can use almost any gpd membrane with your setup as they are mostly universal.
     
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  9. DSC reef

    DSC reef Giant Squid

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    We always learn something new in this hobby. I was told it's imperative to match the membrane with the gpd of the unit. Thanks vinny.
     
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  10. Vinnyboombatz

    Vinnyboombatz Giant Squid

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  11. AZDesertRat

    AZDesertRat Giant Squid

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    If your tap TDS is 600 and the RO only TDS is 14 you are at around 97% rejection rate or removal efficiency which is terrible but could be better. My tap TDS is between 560 and 800 depending on the source blend and my RO only TDS is between 2 and 3 and the membrane is o ver 6 years old. My DI will last around 3-5 times longer than yours based on those results so the cost of a better membrane may be justified. Take a look at the Spectrapure SpectraSelect series 99% guaranteed membranes and matched capillary tube flow restrictors.

    Dow Filmtec membranes and Spectrapure which start out as Dows but are improved upon are all the sam physical size so a 15 to 100 GPD will all fit in your housing but I do not recommend a 10 since it is only 90% efficient versus 96-98% for the 75 or 99% for the SpectraSelect.
     
  12. mdbostwick

    mdbostwick Vlamingii Tang

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    Is this and this what you are talking about?

    Also I think it may have been you that recommended I modify the unit I have, i may be wrong though. It is 6 stages sediment, carbon, carbon, RO, DI, DI. Both DI modules are the type you pack the resin into and they sit horizontally, i will try to get a picture of the unit. If i remember correctly, you recommended I take the last carbon and convert it into the DI so it could take a cartridge. If i am incorrect just let me know, but if you did recommend that I am wondering if there is a thread on how to do this or what i would need to do.

    Thanks for your help.