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Thread: pH rising due to aeration?

  1. Back To Top    #1

    Join Date
    Jul 2016
    Carlsbad, CA

    Question pH rising due to aeration?

    I have seen posts on TFP saying that using bleach will usually not raise your pH, but that using tri-chlor tabs will usually lower pH (because they are so acidic) making it necessary to add pH increaser to counteract this.

    My experience has been the opposite. Back when I was using Tri-Chlor tabs in an in-line chlorinator, as my main method, I found that pH stayed in the normal range 7.4 to 7.6 and that I very rarely had to add acid, and never had to add pH increaser.

    Now that i am using bleach exclusively, I find that pH regularly rises, so I have to add acid a couple times a week. On average, I'm using about 1 to 1.5 gallons of 20 Baume muriatic acid per month, in a 16000 gallon pool. I'm not complaining, but am curious why my pH experience is different. The only explanation I can think of is aeration, since I've heard that tends to increase pH due to outgassing of CO2.

    My pool has a waterfall from the spa with a 1 foot drop to the pool. Part of the return flow goes to the spa and part to the pool, and all the drainage is from the pool. I have a variable speed pump. I run it 10 hours a day on low speed plus 2 hours on high speed (to make my pool vac run effectively). So it gets 2 hours of fairly vigorous aeration per day.

    I find that my TA is tending to go down, probably due to the regular acid dosing I have to do. My fill water has a TA of 100, and my pool TA is down to 60 now. Back when I was using tri-chlor tables and rarely added acid, I found that my TA tended to rise, and it was around 170 before I drained the pool and switched to bleach last spring.

    just curious what everybody's thoughts are on this. I'm not bothered by this, other than the fact that I may have to add baking soda if the TA gets too low.
    16,000 gallon outdoor in-ground 16'x32' plaster pool (built 2002); Pentair Intelliflo VF pump; Jandy Cartridge filter;Rainbow in-line chlorinator (used only when I am away); Hayward 2 wheel suction-side pool cleaner; LARS gas heater, Taylor K-2006 FAS-DPD test kit

  2. Back To Top    #2

    Join Date
    May 2016
    Troy IL

    Re: pH rising due to aeration?

    My thoughts are that you are seeing exactly what should be happening happen with TFP. Now that you've got your TA down to 60 you should see the pH rise slow down....but with a TA up at 100 or more that waterfall aeration is sure to cause pH rise. It wasn't a problem with pucks since they counteract this pH rise, but when you stopped using them you had to counteract it another way (MA). But if you have your TA at the right place you shouldn't have to add MA that often. And if you find yourself fighting high pH, the more you add acid the faster it'll go down, eventually bringing you to an equilibrium.

    20,000 gallon IG Vinyl
    Pentair Tagelus TA60D Sand filter
    Pentair Challenger 1.5HP pump CFII N1 1.5A
    Taylor K-2006-A, Stenner 45MPHP10 auto chlorine feed

  3. Back To Top    #3
    VinDeeLoo's Avatar
    Join Date
    Jun 2016

    Re: pH rising due to aeration?

    Yes, the pH rise is due to aeration. Your TA is not affected by aeration, but lowers due to your MA addition.

    Sent from my iPad using Tapatalk
    7600 gallons ~ AG ~ Summer Waves Cartridge C Filter ~ using pump that came with our Summer Waves 18 x 48 pool ~ Taylor K-2006 (SpeedStir & Sample Sizer) ~ no well water or water restrictions

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