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RO vs DI

Discussion in 'General Discussion' started by Bela, Apr 2, 2009.

  1. Apr 2, 2009 #1
    Bela

    Bela Inactive User

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    So I posted a little while ago about my RO/DI unit. It is working great, I think. I just had a few more questions to those that have them. I set up the DI bypass to my drinking water tank. I tested the TDS today and it is giving me abut 12. I then tested the DI and it is giving me 0, which is what I put in the tank. My question is whether or not 12 TDS is too high now for the RO water. I am thinking it is. The RO I used to get at Hy-Vee tested 5 TDS. Again, the filters are all brand new. Not sure what the issue could be?
    Sorry to resurrect a tapic that I thought was dead/solved, I just don;t want to be doing something wrong.
    ~Bela
     
  2. Apr 2, 2009 #2
    h2so4hurts

    h2so4hurts Inactive User

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    I'm confused. Your RO reading is 12 and your DI is 0? What's wrong with that? You really couldn't ask for better. I drink TDS of 400 water everyday and I'm ok /DesktopModules/ActiveForums/themes/_default/emoticons/wink.gif
     
  3. Apr 2, 2009 #3
    AJ

    AJ Inactive User

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    So if you're asking if 12 TDS is acceptable for the water coming out of your RO before the DI stage, from the people I've talked to, that's fine. I think that it varies from low single digits to upper teens for what's acceptable out of your RO. The DI does the rest.  Now, the higher the number from your RO, the faster you will consume DI resin...

    --AJ
     
  4. Apr 2, 2009 #4
    Bela

    Bela Inactive User

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    I wasn't displeased with it. To elaborate more, I was getting 5 TDS from the RO right around when i first started using the system. I was more concerned with burning out the DI membrane by allowing too much TDS to flow through it.
     
  5. Apr 2, 2009 #5
    Bela

    Bela Inactive User

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    Yeah that resin is what I was not wanting to burn through being that it is the most expensive component to replace. No sense in consuming it more than needed. Anyway, good to know things are normal :)
     
  6. Apr 2, 2009 #6
    h2so4hurts

    h2so4hurts Inactive User

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    It seems pretty normal to me. The numbers off your RO will vary from day to day depending on the quality of water going into it. Also be sure to flush your RO membrane every couple of days just to keep it nice and clean. An RO membrane, if maintained well can last up to 3 years!
     
  7. Apr 2, 2009 #7
    einsteins

    einsteins Experienced Reefkeeper

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    First....what is the TDS of your Tapwater?
    Second....What membrane are you using?

    Those two should give you a TDS that you should be getting off of the membrane.

    For example a Filmtech 75 GPD membrane has a 98% rejection rate,,,so if your tap water has a tds of 200 you should see a TDS of around 4 coming off of that membrane (give or take 2tds)

    Filtech 100 gpd have a rejection rate that is much lower so you will get a higher tds off of the membrane.
    You need to find out what membrane you are using and what its rejection rating is.

    Many ebay units and super cheap units out there come with really cheap membranes and filters (thats one of the ways they keep costs down)

    Hope that helps.....

    eins
     
  8. Apr 2, 2009 #8
    Waverz

    Waverz Expert Reefkeeper

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    Keep in mind water temp and pressure going to the membrane will also be a factor on what your actual TDS should be.
     
  9. Apr 2, 2009 #9
    Bela

    Bela Inactive User

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    Wow, so many replies already. Thanks all, I guess I was worrying over nothing. I just have had no experience with these units and didn;t want to be doing something incorrectly.
    Pressure reads 60-65 psi and temps have been right around 50 degrees.
     
  10. Apr 2, 2009 #10
    jtesdall

    jtesdall Expert Reefkeeper

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    I agree, nothing to worry about here. 0 TDS into the tank is the most important thing. We can go over any of this when you stop by Saturday.
     
  11. Apr 2, 2009 #11
    Bela

    Bela Inactive User

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    TDS of water in is about 150-220... it varies, not sure why so much, but it does.
    The membrane is whatever Air Water and Ice sells. Rated 75gpd
     

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