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Thread: Phosphoric acid & pH

  1. #1
    cygnusecks is offline Established User Thread Analyst cygnusecks 0
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    Default Phosphoric acid & pH

    All,

    I am preparing to seal my paver deck around the pool. Yesterday I applied a solution of "Behr Concrete Etcher & Rust Remover No. 991" to my deck to clean it/dissolve efflorescence and during rinsing a good deal of it was rinsed into the pool. It took 1.75 gallons of the product to finish the job, and I figured it would lower my pH since I would guestimate maybe a 3/4 gallon probably ended up in the pool. Pool is 14k gal inground pebbletec/gunite pool.

    After a few hours or cleaning up and running filter, pH tested normal at 7.6 (i.e. no change). I was a little surprised. My Alk level is 100. Does this sound unreasonable that the pH wouldn't change after 3/4 gal of phosphoric acid was dumped into the pool?

    The MSDS for this stuff is at

    http://www.msdsvault.com/msds_custom...hreg954&ab=991

    It is 30-60% Phosphoric acid.

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    waterbear's Avatar
    waterbear is offline PF Support Team Sniggle Mechanic waterbear 4 stars waterbear 4 stars waterbear 4 stars waterbear 4 stars
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    Default Re: Phosphoric acid & pH

    Phosporic acid is a mild acid but the main reason that is probably didn't affect your pH is that is was neutralized by the calcium carbonate 'efflouressence' that it dissolved which is mildly alkaline. Therefore the water that washed into the pool probably had some calcium and some phosphates in it but was near a neutral pH.
    11.75'x23.75' kidney 6.5K gal IG fiberglass pool/300 gal acrylic spillover spa combo; Aqualogic automation/SWCG; Pentair Clean and Clear 150 cart filter; 1.5 hp uprated 2 spd Pentair Whisperflo pump; PF:17
    Retired pool store and commercial pool maintenance guy.

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    cygnusecks is offline Established User Thread Analyst cygnusecks 0
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    Default Re: Phosphoric acid & pH

    Ah, cool, makes perfect sense waterbear. Great, just what my 500ppm CH-level pool needs -- more calcium!! :-) Soon as I get an accurate read on CH using my PS234 which is theoretically on order, I'm gonna fix the CH level and bring it down some. I'm not sure it's great for the gas heater!

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    waterbear's Avatar
    waterbear is offline PF Support Team Sniggle Mechanic waterbear 4 stars waterbear 4 stars waterbear 4 stars waterbear 4 stars
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    Default Re: Phosphoric acid & pH

    Depends on what you TA is at. If it's at the low end of the recommended range and the CH not above 500 ppm AND you have no visible scaling happening then you might be ok.
    11.75'x23.75' kidney 6.5K gal IG fiberglass pool/300 gal acrylic spillover spa combo; Aqualogic automation/SWCG; Pentair Clean and Clear 150 cart filter; 1.5 hp uprated 2 spd Pentair Whisperflo pump; PF:17
    Retired pool store and commercial pool maintenance guy.

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