Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 3 of 3

Thread: Question Concerning the Amt of MA Required at Different pH

  1. Back To Top    #1

    Join Date
    Jun 2008

    Question Concerning the Amt of MA Required at Different pH

    My water chemistry:

    FC = 5
    TA = 80
    CH = 230
    Borates = 20
    CYA = 65

    When I use the Pool Calculator I get the result that to change the pH from 8.0 to 7.6 I need to add 57 oz of MA.

    To change the pH from 7.4 to 7.0 I need to add 78 oz of MA.

    In the first case a decrease of the pH of .4 requires 57 oz of MA and in the second case a decrease of the pH of .4 requires 78 oz of MA.

    I would have expected that the amount of MA required would have been the same; perhaps it has been too many years since I took chemistry. Can you explain why more MA is required to lower the pH when the starting pH is lower?

    If you watch the pH levels for eye comfort and the CSI index this result implies that you can reduce the amount of MA used by maintaining your pool at a higher pH level.
    30,000 gallon gunite in-ground with a spillover spa, Diving board and water slide
    Hayward 1 HP Super II filter pump, Hayward 24 " Sand Filter Pro Series using zeolite media
    Polaris 380 cleaner with ¾ HP booster pump, Hayward Heatmaster pool heater, AutoPilot DIG-220 Power Supply SC-60 cell
    Testing with the TF-100 Test Kit

  2. Back To Top    #2
    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Question Concerning the Amt of MA Required at Different

    pH is logarithmic. Like the Richter Scale is for earthquakes. pH=7 is ten times more acidic than pH = 8.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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

    Re: Question Concerning the Amt of MA Required at Different

    I don't know of any easy way to say it other than: PH is not at all linear. What is surprising is that it comes out anywhere even close to linear.

    To be rather more technical, PH is actually the negative logarithm (base 10) of the molar concentration of dissolved hydronium ions (H3O+). Several of the factors that affect PH, like buffering by TA and Borates also have non-linear components.

    We recommend keeping PH between 7.5 and 7.8, not because of what you just described, but because of the rate of CO2 outgassing is lower at higher PH.
    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

Posting Permissions

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