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Thread: Pool Numbers

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    Join Date
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    Pool Numbers

    My neighbor opened his in-ground pool yesterday evening. His pool was very clear, but it had a lot of water mold in it. He put 4 lbs of trichlor and 2 dichlor pucks in because that is what he always does. It is 21,100 gallons and has a sand filter. He doesn't have a very good test kit, so I went over and tested it a little bit ago with mine (TF-100). Here are his numbers about 16 hours after adding the chlorine:

    FC-3.5
    CC-3.5
    TA-turned red/pink without doing the last step so not sure what that means (I added the 2 drops of R-
    0007 and 5 drops of R-0008, did not add any R-0009)
    Calcium-I added the R-0010 and R-0011L and it turned Lavender. Wasn't sure what to do with this, so I
    stopped.
    CYA-at least 120, but maybe higher
    PH-The PH was well below 6.8. It actually turned yellow, not pink.

    Any suggestions on what he needs to do with his pool?
    Inground 17 x 34 Rounded Radius Pool, Vinyl Liner, DE Filter, No Saltwater Chlorinator, Approx. 23,750 gallons

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    Re: Pool Numbers

    1. Drain more than half of the water to make his CYA manageable. (50 or so)

    2. VERY SOON, get the pH up into the mid 7"s using 20 mule team borax.

    3. Shock the pool....a process he can follow in Pool School

    4. Disregard the TA and pH until you get 1-3 accomplished

    5. Don't be surprised if your neighbor's eyes glaze over if you explain this to him..........no good deed goes unpunished!

    If you can get him to come on the forum and learn on his own, he will be more likely to follow the methods we teach.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    JasonLion's Avatar
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    Re: Pool Numbers

    Both the PH and TA are extremely low and should be raised right away. You can raise both together with soda ash/washing soda/PH Up or you can raise them separately with borax and baking soda. Either way, get the PH up to at least 7.0 as soon as possible.

    The CYA test in the TF-100 will report ant CYA level above 100 as something right near 100, so the CYA level could be much higher. You can do the CYA test with dilution to get an approximate idea of CYA levels between 100 and 200. Mix one part pool water with an equal amount of tap water, do the CYA test using that, and then multiply the result by two.

    To get rid of the water mold, he/you should shock the pool. Before doing that, the CYA level should be brought down below 100, preferably to something much lower like 50.
    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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    Re: Pool Numbers

    The first post sounds like he should drain first. The second sounds like he should do the PH and TA first. Which way would be better? Thanks for the help and I am trying to get him on here!!!
    Inground 17 x 34 Rounded Radius Pool, Vinyl Liner, DE Filter, No Saltwater Chlorinator, Approx. 23,750 gallons

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    Re: Pool Numbers

    The sequence is okay either way as long as you follow Jason's suggestion to get the pH up in the very near future.....you'll just use a little more borax if you drain first. I would get the pH where it needs to be over the weekend...no later.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  6. Back To Top    #6

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    Re: Pool Numbers

    I tested the CYA using the method desribed and got around 100 again. So, CYA is upwards of 200 I guess. He was home this time and he thinks his pool is looking a lot better. A lot of his water mold that was floating around after brushing last night can't be seen. It might be hard to convince him he needs to drain!
    Inground 17 x 34 Rounded Radius Pool, Vinyl Liner, DE Filter, No Saltwater Chlorinator, Approx. 23,750 gallons

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    Re: Pool Numbers

    With PH and TA so low, how much Borax, Baking soda, or PH plus should he be adding to his pool. I didn't know if the pool calculator takes into account adding the other when it figures up the amounts.
    Inground 17 x 34 Rounded Radius Pool, Vinyl Liner, DE Filter, No Saltwater Chlorinator, Approx. 23,750 gallons

  8. Back To Top    #8

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    Re: Pool Numbers

    The main part of the Pool Calculator really does only one adjustment at a time. For increasing TA and pH together, what I would do is use the "effects of adding chemicals" section near the bottom, see how much of each chem does what, and add it up myself. Then add maybe 2/3 of the result just to be cautious.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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