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Thread: Before I drain a portion of my pool water

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    jgofnj's Avatar
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    Before I drain a portion of my pool water

    I have a few questions before I go ahead a drain my pool water. Before I discovered this great site, I was ignorant and was using the hockey pucks in an automatic chlorine feeder. As a result, my CYA is around 100-110 ppm. I know the most effective and efficient way to lower the CYA is to drain some water. After reading up on draining the pool, I had some concerns because I have a vinyl liner pool. I am OK with taking the slow approach which is to dump a little then fill with fresh water and repeat as necessary to avoid damaging the vinyl liner. But my question is

    1) Should I shut off the skimmer lines and drain from the main drain only so that if I reduce below the skimmer line, it does not take in air?
    2) Or do I leave the skimmer open and not worry about going just below the skimmer opening?
    3) Or do I just drain only enough to not go below the skimmer level (which is only about 5-6 inches)

    Thanks.
    20,000 gal, In-Ground (built in 2007)
    Vinyl lining / 1HP Hayward SuperPump / Hayward Pro-Grid DE Filter / Hayward Gas Heater / Liquid Chlorine,Bleach (4 Gallon Liquidator)
    Dohney Discovery Robot
    Testing Method: TFTestkits/TF-100

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    linen's Avatar
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    Re: Before I drain a portion of my pool water

    Since your cya is so high (how did you determine your value?), you are going to have to replace more than 1/2 of your water if you do it at one time to get down to ~50 ppm cya. Unless your ground water is really high right now, you should be able to safely drain down to 1 ft of water left in your shallow end. If you can isolate your floor drain, I would just pump form there.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    jgofnj's Avatar
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    Re: Before I drain a portion of my pool water

    How did I determine my CYA level of 100-110? Good question. Actually when I ran the test using the TFP test kit I got a reading of 80-90 range. Forgive me for saying this part, but I took some water it to the pool store to see what their reading is, and they said it was 118 ppm. I figured I am in the ballpark of about 100 ppm. But here is the kicker, when I commented on how high the CYA levels were, the guy said it wasn't because the normal range is 30 - 250 ppm!!!! I truly feel sorry for people who rely on pool store money making machines.

    So anyway, I will just remove about 25% and re-test it with my TFP test kit and go fro there. I am not going to rely on the pool store readings.

    Thanks
    20,000 gal, In-Ground (built in 2007)
    Vinyl lining / 1HP Hayward SuperPump / Hayward Pro-Grid DE Filter / Hayward Gas Heater / Liquid Chlorine,Bleach (4 Gallon Liquidator)
    Dohney Discovery Robot
    Testing Method: TFTestkits/TF-100

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    linen's Avatar
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    Re: Before I drain a portion of my pool water

    I would trust you measurements so if we assume 75 ppm cya then draining 1/3 of your water will get you to 50 ppm.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Before I drain a portion of my pool water

    Linen is perfectly correct about being safe down to 1 foot of water in the shallow end. I am just a little on the chicken side of things so I like 33% at a time. 25% at a time is fine, too.

    Trust your TF-100 results, if you did the test in sunlight, with your back to the sun.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    jgofnj's Avatar
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    Re: Before I drain a portion of my pool water

    Thanks Guys! OK I will go with my readings (yes - I did it outside with sun to the back) and dump about 25 - 33%, fill and then see what my reading is from there.
    20,000 gal, In-Ground (built in 2007)
    Vinyl lining / 1HP Hayward SuperPump / Hayward Pro-Grid DE Filter / Hayward Gas Heater / Liquid Chlorine,Bleach (4 Gallon Liquidator)
    Dohney Discovery Robot
    Testing Method: TFTestkits/TF-100

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    GreatCanadian's Avatar
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    Re: Before I drain a portion of my pool water

    I would drain the 1/3. Easier to raise it than lower it.
    13'x22'x52" 8,000 gallon ProSeries Pool with Borates
    Intex 110 pound Sand Filter with Zeobrite, 2650 gph pump, 0.95 hp
    Bestway SWG
    AquaPro ECO500 50,000 BTU heat pump
    GLI Whirlwind Solar Cover Reel, TF-100 Test Kit

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