RO Water

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by Maltese, Feb 23, 2018.

  1. Maltese

    Maltese Member

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    Mr. Farley Holmes 0.3 Tds ro water is good or not ? My tap water is 90 tds. Thank you.
     
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  2. Ludders

    Ludders Active Member R2R Supporter UK Reef Club Member Build Thread Contributor

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  3. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    0.3 is not likely the number. Is it 3 ppm TDS?
     
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  4. Maltese

    Maltese Member

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    First of all i want to excuse me for my belated reply . I attached a picture below showing the Hanna TDS meter RO TDS.jpg[/QUOTE]
     
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  5. Maltese

    Maltese Member

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    Yes, but any help from everyone is appreciated thank you.
     
  6. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    3 ppm TDs.

    It may be OK, but I normally recommend changing the DI when TDS rises above 0 ppm. Depending on what is in your water, when it first rises, it might have substantial ammonia or silicate in it, for example. More of either or both than is in the incoming tap water.
     
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  7. Maltese

    Maltese Member

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    My RO filters are new even the membrane i renewed . I don't have a DI system, only an RO system. May be i go for a new one with DI system. Thank you Mr. Randy for your support.
     
  8. Shores805

    Shores805 Rogue R2R Supporter

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    Just curious, what’s your take on acceptable RO values? I’ve studied this thoroughly and have heard conflicting vantage points on those who claim they’re RO is truly at zero. Also, if you don’t mind weighing in your opinions on chloramine filters. I recall @AZDesertRat telling me they’re essentially worthlessx however Spectrapure and others recommend them.(for those of us with chloramine in our municipal tap.)
     
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  9. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Are you asking about RO water, or RO/DI?

    Neither are ever truly 0.0000000 ppm TDs, but 0 ppm TDS is normally attained.

    If you get chloramine in your final effluent (easily tested with a cheap chlorine kit since it detects chlorine too) it may be worth getting a special carbon block. But when I surveyed folks and sent around a chloramine kit to them for evluations, hardly anyone (myself included) needed any special carbon block:

    Chloramine and the Reef Aquarium - Reefkeeping.com
    http://reefkeeping.com/issues/2003-11/rhf/feature/index.htm

    Removing Chloramine With Activated Carbon: Does it Really Work?

    There has been much debate over whether commercial RO/DI systems used by aquarists are actually removing chloramine in adequate quantity. The concern is not whether they can theoretically do so, but whether the actual units allow sufficient contact time between the water and the activated carbon for the units to do an adequate job.

    I have been using a Spectrapure RO/DI system (CSP25DI) for years, and my water does contain chloramine, so naturally I was interested to know if it was up to the task. In discussing the issue with Charles Mitsis, President of Spectrapure, he said that my water was among the most difficult to successfully remove chloramine from because the pH was high, and he was not sure that the unit was adequate. The reasons for being concerned were that:

    1. Monochloramine is the most difficult of the three chloramine species to remove because it is small (allowing it to pass through a reverse osmosis membrane).
    2. Monochloramine is the most chemically stable of the chloramine species, so is the hardest to break down (as on activated carbon).
    3. Monochloramine predominates over the other forms in tap water at pH above 7 (dichloramine predominates at pH 4-7).
    4. The pores of the activated carbon may become plugged with sediment over time, reducing the effectiveness of the carbon at breaking apart chloramine.
    5. At high pH, the pores of the RO membrane can swell, resulting in poorer rejection of impurities.
    With this as the backdrop, I set about organizing a round of testing by aquarists to see if their commercially-available systems were adequately removing chloramine.

    First, I selected a single, high quality test method for participants to use: the Hach CN-70 kit described above. I then asked aquarists to test several things:

    1. The free and total chlorine in their tap water after letting it run for a while.
    2. The free and total chlorine in their RO reject water.
    3. The free and total chlorine in their finished RO/DI water.
    4. The pH of the tap water.
    In my case, for example, I had the following results:

    Tap water:
    pH ~9
    Total Chlorine: 0.4-0.5 ppm one day, 0.08 ppm on a second day.
    Free chlorine: <0.01 ppm (effectively all of the total chlorine was chloramine)

    RO Reject water:
    Total Chlorine: 0.02 ppm
    Free chlorine: <0.01 ppm

    Final RO/DI water:
    Total Chlorine: <0.01 ppm

    Consequently, within the capabilities of the Hach test kit (0.01 ppm), there is no chloramine getting through the system. A small amount does appear to get past the carbon to the RO waste water, but it does not get through the RO membrane and DI resin.

    A similar set of data (more or less complete) was collected from about 20 aquarists in different parts of the country. These included systems that were stated to have a capacity of 25-100 gallons per day, the higher volume systems being especially interesting because the contact time with the carbon might be shorter. All but one had similar results to those reported here. The anomalous report produced the following results:

    Tap Water:
    pH 8.2
    Total Chlorine: >3.5 ppm
    Free Chlorine: >3.5 ppm

    Filtered Tap Water: (single cartridge under sink, cold water side)
    Total Chlorine: 0.7 ppm
    Free Chlorine: 0.38 ppm

    RO water: (11 month old cartridges)
    Total Chlorine: 0.16 ppm
    Free Chlorine: 0.06 ppm

    RO/DI water: (11 month old cartridges)
    Total Chlorine: 0.04 ppm
    Free Chlorine: 0.02 ppm

    RO/DI water: (Fresh cartridges)
    Total Chlorine: <0.01 ppm
    Free Chlorine: <0.01 ppm

    In short, his tap water chloramine (and chlorine) levels were quite high. His old carbon and sediment cartridges were not quite up to the task, but when replaced, were adequate to remove all of the chloramine. Note that the 11 month old cartridges were still producing 0-1 ppm TDS RO/DI water.
     
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  10. Maltese

    Maltese Member

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    Thank you Mr. Farley this quote that you made is incredibly informative . Here where i live tap water is high in chlorine you can smell it. and it is high in silicates too. I've just tested the silicates.
    Exactly as you told me in the other posts. Really appreciate Mr. Randy you went exactly on the head of the needle !
     
  11. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    You’re welcome.

    Happy Reefing.
     
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  12. Maltese

    Maltese Member

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    Thankyou Mr. Randy.
     
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