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Thread: Acid drop Test?

  1. Back To Top    #1

    Join Date
    Jul 2014

    Acid drop Test?

    I am new to pools, having just put in a 35,000 gal in-ground pool with Pebble Fina finish. The contract comes with 30 days of free pool service so I am using a "pool guy" for now. They started the pool up with a "hot start", adding acid to the pool to mildly etch the plaster which allows the quartz flecks to show through the plaster and the finish to even out. They neutralized the acid after 72 hrs and started up the pool, using trichlor tablets in the dispenser. Since then (18 days), the "pool guy" has been out once a week. In between his visits the PH spikes to over 8.2 (K-1000 kit) and remains up several days until he shows up to add more acid.

    Not only does he assure me that this high PH is normal for a new pool (plaster curing), but that without an "acid demand test", I wouldn't know how much acid to add to properly bring the PH down to a reasonable level. He claimed that for a given PH level (e.g. 8.2 in my case) , the "acid drop test" might well indicate a requirement for different amounts of acid depending on any given day and any given test. He claimed that without the "acid drop test" it is impossible to accurately add the appropriate amount of acid. So for my new pool with 35,000 gals and 8.2 PH he added ONE PINT of acid.

    Questions -

    1) With a given PH reading, known pool size in gallons, and known Muriatic acid strength, don't the pool charts or pool calculators clearly show how much acid to add? More importantly, how could the acid demand test offer different results from test to test as he claims when the measured PH has remained constant? (phase of the moon, first day of summer, what? ) What variable am I missing that would require the religious use of this test rather than careful attention to the charts?

    1) Don't I run the risk of scaling or hydration leaving the PH at 8.2 or higher for several days at a time in a new pool? They have already botched the "hot start job", leaving the pool coloring very irregular, blotchy and stained-like.

    Pool numbers: (TF-100)

    FC = 0.0-1.0
    CC = varies 0.0-.5
    PH = 8.0-8.2 (except for pool guy's weekly acid additions)
    TA = 40
    CYA < 20

    Thank you all for your helpful advice.

  2. Back To Top    #2
    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Acid drop Test?

    Wow ... another pool "expert" who has no idea about pool chemistry.

    1) PoolMath will tell you how much acid is required to lower from 8.2 to say 7.5 (make sure you enter your current TA). The only issue is that the pH may actually be higher than 8.2 to start with. To combat this. You add acid targeting 7.5 (or whatever) from 8.2. Circulate for 30 minutes, and then retest to see the new pH. If it is still high, repeat until you are at your target. The drop acid demand test will speed this iterative process up because the number of drops can give you a better idea how high the pH really is to start with ... but it is usually not a good idea to make massive changes all at once anyway.

    2) I would not want my pH that high. You might ask the builder whether it is ok for you to lower the pH into range ... they are the warranty issuer I imagine.

    It is quite often that members here will take much better care of the pool that the "start-up" people who only show up once a week. Ask if you can take over now and show him the door.
    Jason, TFP Moderator
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