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Thread: Green Pool with High Chlorine

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    Green Pool with High Chlorine

    Our 13,000 gallon 24ft above ground pool with a cartridge filter has been green for almost 10 days. It turned green after leaving the cover on for a 2 days during a heat wave.

    In the beginning we poured bleach in it to try and kill the algae, however, we got our water tested at a pool store and they said our chlorine was sky high and the algae had grown immune to the chlorine and there was nothing we could do.

    We've been cleaning and changing the filter every few hours and the water is looking a little better, but still really green. Is there anything else we can do to get the pool back to blue?

    the levels as of today:
    FAC - 10
    TAC - 10
    CH - 250
    CYA - 90
    TA - 80
    pH - 7.8
    Copper - 0
    Iron - 0
    TDS - 1100
    Pho - 200

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    Re: Green Pool with High Chlorine

    You need to get your chlorine levels higher with CYA being that high. In fact you may want to drain part of the pool to get the CYA level down first then add your chlorine after refilling. Replace with fresh water and only use bleach or liquid chlorine going forward. The Chlorine/CYA chart at you current readings would require 35 ppm FC to get the pool to shock level. That's going to be near impossible to maintain. Here is a link to the chart:

    Pool School - Chlorine / CYA Chart

    I'd drain a 1/3 or so of the water, refill, measure CYA and then add chlorine to shock level. You can calculate how much bleach/liquid chlorine you'll need with the pool math:

    http://www.troublefreepool.com/calc.html

    Edit: Whoever told you algae grows immune to chlorine should not be giving you advice on pool maintenance.
    20500 gal Pebble Tec ingroud. Hayward S310T Sand Filter, 3/4 HP Hayward pump, Hayward Poolvergnuegen, Hayward AQR15 SWG.

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    pabeader's Avatar
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    Re: Green Pool with High Chlorine

    Welcome to TFPC! You will be glad you stopped in. First things first, you need to get a good test kit; either a TF-100 with XL option or a K-2006C, and start testing your pool yourself. We place no faith in pool $tore testing for the exact reason you are stating.

    If we were to accept their numbers, you do not have enough chlorine in your pool to make a dent in the algae problem.

    Here is a link to the chart that explains it all. Pool School - Chlorine / CYA Chart
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    jeffchap's Avatar
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    Re: Green Pool with High Chlorine

    Hoo-boy! Where to start?

    I'm on my phone, so I'm going to keep this short and sweet. I'm sure someone else will be along shortly to give you the full rundown. But the bottom line is, your pool store does not understand the relationship between CYA and FC. With your CYA at 90, which is higher than we like, your minimum FC level to prevent algae is 6.5 and your target should be 10. Now that you have algae, the shock level you need to reach AND MAINTAIN is 36 ppm until all the algae is gone and you pass what we call an overnight chlorine loss test (OCLT).

    Keep adding bleach until you get that FC up to 36 and keep it there. And yes, it is safe to swim in at that level as long as you can see the bottom of the pool.


    Also, if you don't have one, you need to get a test kit that includes a CYA test and a FAS-DPD test that measures FC up to 50 ppm. Both of those measurements are critical to the TFP method, and even more so now that you have an algae bloom. Pool store testing and test strips are simply not reliable.

    I'll turn you over to the experts now.
    25000 gallon free-form gunite
    Jandy Stealth pump/CL340 cartridge filter
    Pentair IC40 SWG
    Pentair MasterTemp 250HD heater
    Jandy AquaLink RS automation

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    jwhop3's Avatar
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    Re: Green Pool with High Chlorine

    Quote Originally Posted by Krt View Post
    and they said our chlorine was sky high and the algae had grown immune to the chlorine and there was nothing we could do.
    Every time I think a pool store could not make a dumber analysis and prescription, they go and prove me wrong.

    Who knew algae had an advanced immune system???
    14,000 gallon Fox Lagoon, ingound vinyl
    PacFab Sand filter
    installed April, 2002
    Frog inline chlorinator
    Town water

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    jwhop3's Avatar
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    Re: Green Pool with High Chlorine

    How are you sanitizing? Are you using bleach, per the BBB method, or are you using shock packets? Keep in mind, those bags of shock contain CYA. Unless you are dealing with extreme conditions, you should never need more than 50 ppm for CYA.
    14,000 gallon Fox Lagoon, ingound vinyl
    PacFab Sand filter
    installed April, 2002
    Frog inline chlorinator
    Town water

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    Kiss4aFrog's Avatar
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    Re: Green Pool with High Chlorine

    Welcome to TFP krt

    Please add your pool and equipment info to your signature as outlined here - - > Pool School - Getting Started

    If your CYA is at 90 and you do not have a Salt Water Chlorine Generator you need to dump about 1/2 to 2/3 of the water out before you waste any more money on adding chemicals (bleach) to clear it up. Don't use any algaecide, please.
    Non SWCG pool you should be around 30-40 CYA for Ohio and depending on where you end up after the refill you'll likely need to reach and MAINTAIN at least 12-20 ppm FC (chlorine) to kill off the algae and start to see blue water again. Those numbers are just approximations and testing and using the charts will tell you exactly what you need. The trick is to test often at first and maintain a high level of chlorine to kill the algae and not raise it and let it fall and then raise it again.

    After the refill your FC will be under 10 and I'd test that pH again and bring it down closer to 7.2 before you start the slam. pH isn't accurate when FC is above 10ppm.
    '70s IG Vinyl 32K gal, Lazy L, Hayward SuperPump 1.5hp 120V, S240 Sand Filter W/DE
    Solar Blanket, Well Water, Borax Added, TF-100 tester. ? too cold
    1979, 275gal Conway Emerald Spa P-100-2, ES-2 Spa Pack, bromine floater, indoor
    TF-100, Best test kit - TFTestkits.net
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    Re: Green Pool with High Chlorine

    Thank you so much everyone for all your help! I've learned more about my pool in the past few days than I have in years of going to the pool store.

    I ordered the TF-100 test kit and am planning on doing the testing myself from now on!

    I think our CYA might have gotten so high from the chlorine tablets that we've been floating in the pool in addition to adding the bleach.

    We drained more than 1/3 of the pool and refilled it. We took a sample back to the pool store while we are waiting for the test kit to ship in hopes of getting a head start on clearing up the pool, but the test still showed the CYA at 90. Should we try to bring it to shock FC with the CYA as it is now or should I wait until I get my test kit in the mail and drain the pool again from there?
    13,500 gallon above ground pool
    Cartridge Filter
    Installed in 2000

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    Mr Bruce's Avatar
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    Re: Green Pool with High Chlorine

    Pool stores are notoriously bad at testing CYA. You may be dumping water unnecessarily, just add 1/2 gallon of bleach per day with the pump running until your test kit comes.
    32K gallon Plaster - 1hp Hayward 2 speed Super Pump - Hayward S200 Sand Filter - TF100XL
    Test Kits - Pool Math - Chlorine/CYA/Target/Slam Chart

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