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Thread: PH Swings and pool damage

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    H2O_Keeper's Avatar
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    PH Swings and pool damage

    I was having a discussion the other day with a chemical engineer that is responsible for water treatement for a manufacturing plant. We were talking pools and I was sharing some of the techniques on this forum about the lower alkalinity by the add acid/aerate and the borax/add MA thing to balance water. He was very concerned that I should not go through these activities because it is very hard on the equipment, liner, heaters, etc.

    I explained we were only talking about moving PH less than one point back and forth through these processes. He cited me several examples in their plant where they went through extreme wear on componets with a one degree swing. All even within a few weeks of these swings.

    I realize they are probably dealing with more pressure and volume than we are with our pools but does anyone have any bad experiences with doing these things and wear? Should we be concerned?
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    JasonLion's Avatar
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    Re: PH Swings and pool damage

    The main risk is if you miscalculate or get sloppy and let the PH get way to low or way too high. If you keep PH between 7.0 and 7.8 you will not have any problems. Even if you go outside that range you often won't have problems. Swimming pools and their chemisty are both designed to give you lots of leway.
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    Re: PH Swings and pool damage

    Quote Originally Posted by H2O_Keeper
    I was having a discussion the other day with a chemical engineer that is responsible for water treatement for a manufacturing plant. We were talking pools and I was sharing some of the techniques on this forum about the lower alkalinity by the add acid/aerate and the borax/add MA thing to balance water. He was very concerned that I should not go through these activities because it is very hard on the equipment, liner, heaters, etc.

    I explained we were only talking about moving PH less than one point back and forth through these processes. He cited me several examples in their plant where they went through extreme wear on componets with a one degree swing. All even within a few weeks of these swings.

    I realize they are probably dealing with more pressure and volume than we are with our pools but does anyone have any bad experiences with doing these things and wear? Should we be concerned?
    Did he understand that you were talking about lowering the pH from 7.5 to 7.0 and not lower and that this is for a period of days up to perhaps a week and not longer? That's only a half point difference, not one point, and 7.0 is quite a bit different than 6.0. Also, as you point out, water treatment manufacturing processes are quite different usually exposing containers to very high chlorine levels, not moderated by CYA, so are more corrosive to begin with by orders-of-magnitude and more affected by pH swings.

    The practical experience with pools is that many have been exposed to quite low pH levels due to use of Trichlor tabs without checking on pH and even in such extreme situations it has taken time for damage to occur, mostly to copper heat exchangers first and eventually to plaster. However, the more rapid (and we're talking months) corrosion in these situations had pH down to 5 or below. There is no question that one wants to avoid lower pH, but going to 7.0 during a relatively brief "lowering TA" procedure isn't very risky.

    Richard
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    H2O_Keeper's Avatar
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    Re: PH Swings and pool damage

    Did not realize nor think about the no CYA factor in their water. They run basically the same as a pool 7.0 to 7.5 and have Chlorination going on up to 30FC levels for breif periods. He was saying that if they get very much swing even within this range of 7.0 to 7.5 it causes a lot of wear and tear on the equipment. They now pretreat the water for a consistent PH before the superchlorination.

    I realize its neutral within this range and one wouldnt think it should matter much but in their process it does.

    I sincerely did not think it was an issue except possibly to heat exchangers, thats why I asked the question. I dont plan to go below a PH of 7.2, thus no risk. Thanks for the feedback.

    BTW a few weeks ago I just did my first Acid/Aeration technique to lower TA, it worked, cool trick! I asked my local pool store how to lower TA last fall and they told me to do a partial drain. Cost of $5 (MA) and a turned up return eye was a lot cheaper than the water and sewer bill I would of had doing their way.
    21K Gal, IG, Vinyl, Bleach-Borax-Baking Soda, 3/4HP Hayward pump, Hayward sand filter, 200,000BTU Heater, TF100 Testkit
    "All that we are arises with our thoughts." - Buddha
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    JasonLion's Avatar
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    Re: PH Swings and pool damage

    An FC level of 30 with no CYA has a lot of potential for corrosion and would be very sensitive to the PH. The moment you add CYA everything changes, the PH sensitivity drops dramatically, the effective chlorine level is far lower, and corrosion becomes almost impossible.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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