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Thread: Help designing an experiment?

  1. Back To Top    #1

    In the Industry

    Join Date
    May 2009

    Help designing an experiment?

    I'm surrounded by veterans that insist on first-hand experience with vinyl damaged by untreated soft water.

    So I'm going to put my employee discount to good use and design an experiment. Unless you all tell me that it's not feasible. I'm not looking to publish a paper or anything - just for my own peace of mind.

    Yes, I know that that there's no reason whatsoever besides aforementioned industry guidelines to think that water with a low level of calcium saturation would damage vinyl.

    So -

    1) Fill two translucent milk jugs with tap water.
    2) Adjust to something reasonable for pool-typical water balance:
    FC/TC: 3-5
    PH: 7.4-7.6 (comes out of the tap this way)
    TA: 100
    CYA: 50

    3) Leave one jug at fill-water CH (about 30.) Adjust second jug to 250ppm.
    4) Drop a small piece of vinyl liner in each jug and leave them outside for a week. Keep aforelisted numbers in range.

    And wah-lah.


    1) Will putting the caps back on the jugs and shaking them around every day adequately represent circulation?
    2) Will test strips be accurate enough for the purpose of this test? I foresee problems with removing enough water from the
    jugs for several DPD tests each day.
    3) Is a week long enough?
    4) Will this tell me anything useful at all?

    Thanks, mysterious internet geniuses.

  2. Back To Top    #2

    Re: Help designing an experiment?

    Quote Originally Posted by seilsel
    I'm surrounded by veterans that insist on first-hand experience with vinyl damaged by untreated soft water.
    AND I will bet that they swear to lower pH you walk acid around the perimieter of the pool with the pump running and to lower TA you 'slug' acid in the deep end with the pump off!
    This myth is firmly entrenched yet is totally untrue and there has even been a scientific paper published to debunk it! Yet this myth lives one! ... Column.pdf

    Or how about the one that CYA sinks to the bottom of the pool (or floats in the top 6 inches of water--I've heard it both ways! I've even heard it being taught in a CPO course!) and that to quickly remove the CYA drain from the bottom drain only (or from the skimmer only, depending on who is telling this little lie!) See if any of these "veterens" buys into this one!

    I could go on but you get the idea.

    Low pH is the only thing that will ruin a vinyl liner by leaching out plasticizers and softening the vinyl. Calcium has NO effect on vinyl at all (other than forming scale deposits on it when the water balance is off!)

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

    Re: Help designing an experiment?

    Your setup is fine. I would leave the lids off. Test strips ought to be good enough, if you balance the water with a drop kit the first time, before splitting it between the jugs, and then just use test strips for daily testing. But a week is not long enough. You would need months to convince me of anything, and possibly years to convince someone skeptical.
    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

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