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

Thread: Sorry I was trying to add to my post below...

  1. Back To Top    #1

    Join Date
    Jun 2007
    Location
    South Central Oklahoma
    Posts
    10

    Sorry I was trying to add to my post below...

    Using the calculator, I surmised I needed 110 oz of Borax and 4 gallons of 6% bleach to get to 7.4 PH and 12ppm CL. I added the bleach and it's at 12ppm. WOOHOO!!! But I added 76oz of Borax and my PH may have risen to 7.0 It's hard to tell on my red phenol test. It looks to be between the 6.8 and 7.2 color. I get the same results with the 6 way strip test from Walmart. Any ideas? From the calculator 77 oz of Borax should have raised my PH to 7.2. What am I missing?
    --Guest Too
    IG liner, Sand Filter, Polaris 360, 18x36 oval, 29,000 gallons

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887
    Pools don't always react the way you might expect. Simply retest, recalculate and try again. When making large changes it is often best to go in several steps, adding only part of the calculated amount, and retest after each addition to see where you are. Over time you will get a feel for how your particular pool reacts to the chemicals you typically use and be able to adjust the amounts based on experience.

    There are several possible causes for inacruracies in the calculations of how much to add. First, the usual PH test will show PH values below 6.8 as 6.8. So your PH could have been quite low and you wouldn't be able to tell just how low. Second, PH changes depend on many different factors. It can take more or less acid/base to change the PH at extremes of PH or with different alkalinity levels. Only Richard's Pool Equations spreadsheet fully models some of the more complex factors, and it is not designed for ease of use. Third, there are always measurement uncertianties, the PH test can read slightly wrong in either direction, you may not know the volume of your pool exactly, the potency of the chemicals can vary, etc so the amounts calculated will never be exact.
    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

  3. Back To Top    #3

    Join Date
    Jun 2007
    Location
    South Central Oklahoma
    Posts
    10

    Thanks!

    I hadn't thought that the test would be reading lower than 6.8 as 6.8. I also never thought of different potencies of ingredients. Sometimes I get tunnel vision. I have a lot of people coming over to use the pool so I am a little impatient get it looking good. I haven't seen Richard's calculator can you point me to it. I probably can't use it but I'd like to see it.

    Thanks for your help! Have a Happy Fourth!
    --Guest Too
    IG liner, Sand Filter, Polaris 360, 18x36 oval, 29,000 gallons

  4. Back To Top    #4
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,887
    There is a link to Richard's Pool Equations spreadsheet towards the end of the first post in this thread.
    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

  5. Back To Top    #5

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,085
    Because of the carbonate pH buffering system in your pool, it takes a lot more acid or base to move the pH when the pH is low than when it is moderate (and then decreases again when it is high).

    For example, in a 21,000 gallon pool such as yours and assuming a TA level of 100 ppm and 0 ppm Borates initially, 76 ounces (one box) of Borax will change the pH:

    6.8 to 6.95 or an increase of 0.15
    7.0 to 7.22 or an increase of 0.22
    7.2 to 7.53 or an increase of 0.33
    7.4 to 7.86 or an increase of 0.46
    7.6 to 8.13 or an increase of 0.53
    7.8 to 8.30 or an increase of 0.50
    8.0 to 8.42 or an increase of 0.42

    The same effect is seen adding 3 cups of Muriatic Acid (31.45% Hydrochloric Acid) to your pool:

    7.0 to 6.89 or a decrease of 0.11
    7.2 to 7.05 or a decrease of 0.15
    7.4 to 7.19 or a decrease of 0.21
    7.6 to 7.33 or a decrease of 0.27
    7.8 to 7.45 or a decrease of 0.35
    8.0 to 7.58 or a decrease of 0.42

    Richard
    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
  •