Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 5 of 5

Thread: Sulfates - what's the problem?

  1. Back To Top    #1
    Melt In The Sun's Avatar
    Join Date
    Oct 2009
    Location
    Tucson, AZ
    Posts
    3,899

    Sulfates - what's the problem?

    Generally, the use of "dry acid" is not recommended on this site because it adds sulfates to your water. What's bad about sulfates Since TDS is well-established as a non-issue, I can think of two possible things:

    1. "montezuma's revenge" - politely called "gastric distress", is usually pathogen-related but can be caused by drinking water with several hundred ppm sulfate, if your body is not used to it. High sulfate will also make the water taste bad (not sure about the levels required for this).

    2. "gypsum scaling" - I don't know if this is even possible. It would involve CaSO4 * 2H2O (gypsum) forming due to high CH and sulfates. Technically possible I guess, but gypsum is about 15x more soluble in water than calcite (normal calcium scale).

    Is there something obvious I'm missing? Seems like the water taste would be the most serious of these.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
    TF Test Kits -- PoolMath -- Pool School
    Make each day your masterpiece. - John Wooden

  2. Back To Top    #2

    Join Date
    Feb 2008
    Location
    Denton, TX
    Posts
    5,061

    Re: Sulfates - what's the problem?

    What an excellent question.

    Paging chem geek.

  3. Back To Top    #3
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Sulfates - what's the problem?

    High sulfate levels can damage the SWG cell plates. Unfortunately, I don't know how high the level needs to be before there is a problem. It also seems reasonable to assume that different brands may have different levels of sensitivity.

    Sulfates have also been implicated in plaster damage, though again the exact levels where problems start is unknown. Sulfate damage to concrete at high sulfate levels is well documented, but relatively little information is available about the effects of lower level exposure on plaster.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  4. Back To Top    #4
    Melt In The Sun's Avatar
    Join Date
    Oct 2009
    Location
    Tucson, AZ
    Posts
    3,899

    Re: Sulfates - what's the problem?

    Ah, the concrete issue makes sense. I didn't think of that.

    So for non-SWG, non-plaster pools??
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
    TF Test Kits -- PoolMath -- Pool School
    Make each day your masterpiece. - John Wooden

  5. Back To Top    #5

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Sulfates - what's the problem?

    The concrete/stone damage comes from the fact that magnesium sulfate (and to some degree, sodium sulfate) has extremely high recrystallization pressure, mostly due to the much higher supersaturation achievable compared to regular sodium chloride salt. See this paper for more detailed info (unfortunately, you have to buy it).

    As for calcium sulfate "scaling", it takes very high CH and sulfate levels for this to occur. At 500 ppm CH, it would take about 2000 ppm sulfate for scaling to even theoretically begin. At 1000 ppm CH, it would take around 900 ppm sulfate.

    In an non-SWG pool, we're just being conservative. In an SWG pool, the SWG manufacturers describe problems with sulfate, but unfortunately they don't give a specific level at which problems occur or at what rate they occur.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •