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Thread: Confused about ideal pH

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    tfoggo's Avatar
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    Confused about ideal pH

    I notice that the Pool School's recommended pH level is 7.5-7.8.

    Everything else I've ever seen (pool chemical labels, pool equipment manuals, web articles etc.) suggests it should be 7.2-7.6 with 7.4 being optimum, and have consequently spent a lot of time and money trying to keep my pH inside those parameters (it tends to drift towards the high 7s)!

    Is this a climate/temperature thing (I'm in the UK) or have I just been suckered into buying more 'pH Minus' than I really need?!

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    borjis's Avatar
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    Re: Confused about ideal pH

    7.2 - 7.8 should be safe to swim in and for most equipment, but I aim for 7.5 because that's roughly the ph of the human eye/tears is.

    my 002 cents.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
    (1.5 HP motor) Raypak PR266AEN (266k btu) gas heater. TF-100 Test Kit.
    Dolphin E10 Cleaning Robot.

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    duraleigh's Avatar
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    Re: Confused about ideal pH

    Actually, 7.2 - 7.8 is just fine. There is more latitude in pH than folks think.

    BTW, you can substitute muriatic acid for pH minus....not sure if it saves you money in UK.....it does in US
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    tfoggo's Avatar
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    Re: Confused about ideal pH

    Thanks both. Very helpful!

    All the best.

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    JoyfulNoise's Avatar
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    Re: Confused about ideal pH

    The 7.4 optimal numbers comes from the mistaken idea that your pool water needs to be at a pH close to human tears. It's basically pseudoscientific poppycock. Your tears are perfectly capable of buffering pool water anywhere in the 7 range. Irritated eyes comes from combined chlorine being too high and rubbing ones eyes after emerging from under water.

    So the optimal pool pH is anywhere in the 7 range where your pool water naturally wants to settle at. For many pools, you need to lower TA to keep pH rise under control. My TA is 50ppm and I have 50ppm borates in my pool water. I never lower my pH below 7.6 (unless I'm trying to actively lower TA) and I don't add acid until my pH rises above 7.8. My pH will hang at 7.7 for well over 10-12 days and I typically add acid about once every 14 days or so.

    pH Down is sodium bisulfate. It's not generally recommended to use here because you can build up sulfates in your pool water which are detrimental to plaster and SWG cells. Muriatic acid may not be generally available in the UK, but if it is, it's a better choice.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    tfoggo's Avatar
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    Re: Confused about ideal pH

    Brilliant. Thank you.

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