Low TDS, high alk.

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by Earl Karl, Feb 27, 2018.

Tags:
  1. Earl Karl

    Earl Karl Active Member

    Joined:
    Jul 29, 2017
    Messages:
    258
    Likes Received:
    86
    So my RO/DI water is very weird. The TDS comes out at 2-3 ppm (due to terrible water), but also comes out with high carbonate hardness, which is 8-9 DkH. Right now my water is 3 ppm and 8 DkH. This test has been done by many test kits, including the LFS testing it. However, according to @Randy Holmes-Farley, this is probably not possible. Can someone explain this?
     
    Tags:

  2. Randy Holmes-Farley

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

    Joined:
    Sep 5, 2014
    Messages:
    30,560
    Likes Received:
    18,137
    Location:
    Arlington, Massachusetts, United States
    You earlier said 0 ppm, which is impossible.

    As a rough test, 3 ppm tds is roughly 3 mg/l of some salt. Assuming it is nothing but sodium bicarbonate (which itself is impossible, but assume it is) then 3 mg/l is 0.04 mM = 0.04 meq/ L = 0.1 dKH.

    So it is still not possible and must be alk test error or tds measurement error.
     
    Brew12 likes this.
  3. Brew12

    Brew12 Electrical Gru Staff Member Team R2R R2R Supporter R2R Excellence Award Reef Tank 365 Partner Member 2018 Article Contributor Build Thread Contributor North Alabama Reef Club

    Joined:
    Aug 14, 2016
    Messages:
    14,320
    Likes Received:
    25,917
    Location:
    Decatur, AL
    Has to be testing error. Alkalinity is a dissolved solid and will read on a TDS meter.

    I don't know enough about the way Alk test kits work to know if it is possible for a small amount of contaminant to show up as high alkalinity. Regardless, one or the other isn't accurate.
     
  4. Earl Karl

    Earl Karl Active Member

    Joined:
    Jul 29, 2017
    Messages:
    258
    Likes Received:
    86
    Just checked with my LFS. Alk test says 8 DkH but tds is 260... whoops. Guess I need a new tds meter lol. My tap comes in at 500. So, my ro/di system is terrible, well it is old so it served its purpose. Time to get a new one I guess. Dam.
    I don't know if I can trust any digital meter anymore.
     
  5. Randy Holmes-Farley

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

    Joined:
    Sep 5, 2014
    Messages:
    30,560
    Likes Received:
    18,137
    Location:
    Arlington, Massachusetts, United States
    Yes, it sounds like there's an issue with it. Does it read 0 ppm TDS in air?
     
  6. Earl Karl

    Earl Karl Active Member

    Joined:
    Jul 29, 2017
    Messages:
    258
    Likes Received:
    86
    Yeah, it still reads 0 in the air.
     
  7. Randy Holmes-Farley

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

    Joined:
    Sep 5, 2014
    Messages:
    30,560
    Likes Received:
    18,137
    Location:
    Arlington, Massachusetts, United States
Draft saved Draft deleted

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice
Loading...