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Thread: Using Bleach in the Pool

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    CarlD's Avatar
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    Default Re: Using Bleach in the Pool

    It's impossible to tell without good test numbers. You'll need to get chlorine levels (both free--FC and combined-CC), pH, Total Alkalinity (TA), and Stabilizer/CYA. If it's a concrete or other hard material (not vinyl), you'll need Calcium Hardness (CH) as well.

    The "Best Guess" table tells you what level of Free Chlorine you need, relative to your stabilizer level. But how much to add? Well there's a formula, but the shortcut is that one gallon of 6% bleach will add about 2.4 ppm of Free Chlorine to your pool. That doesn't mean it will RAISE your FC level that much, at least not for long...algae may break it down. 12% liquid chlorine (sometimes called Liquid Shock) will add double that per gallon, or 4.8ppm.

    The best investment you can make is the $50 to $70 for a Taylor FAS-DPD full test kit, the K-2006 or K-2006C. It's not on my sig right now but is on Pooldoc's and on some of the other mods. The kit will pay for itself hundreds of times over and all the test chems ("reagents") are replaceable.
    Carl

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    Default Re: Using Bleach in the Pool

    In order to follow the link for the test kits, you'll have to log out, go to the main forum page, and then find any post made by myself, Watermom, or Pooldoc--new subscribers usually can't follow the links from here while logged in until Ben has completed the registration process.


    Janet

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    Default Re: Using Bleach in the Pool

    As of last night the PH is at 7.6, Chlorine 3.0, the CYA test I was not able to administer, because the test kit I inherited is missing that componnet right now. I used the test strip, which agreed with the test kit #s, and gave me a "very high" stabilizer reading or 150.

    I am told the pool is 25,000 gallons, the filter is a Hayward sand filter S220T, with a Hayward super pump 1.0 HP.

    Pool is cloudy. Seems to have lots of dead algae in it, which moves/billows up when touched and is no longer clingning to the walls or floor. I suppose I will have to vacuum to waste again tomorrow and see what happens.

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    Default Re: Using Bleach in the Pool

    If you see the filter pressure rising, then the filter is doing its job in filtering out the dead algae. Remember, chlorine kills it, then the filter (or vac'ing to waste) removes it. However, you won't know if you've killed it all off until you can test chlorine after the sun is off the pool, and the next morning before the sun is on the pool, and lose less than 1 ppm of chlorine in the process. However, to do that, you are going to need drop-based testing--strips simply are not accurate or reliable enough to use for this purpose. Also, strips do a very, very poor job of measuring CYA--they can usually tell you if there is, or is not, CYA in the pool, but you need an accurate CYA level before I can begin to tell you where your chlorine level needs to be for shocking purposes,. The Best Guess table that Carl referenced above will explain that more fully, but in order to access it you need to log out to the main forum page, to go the "Using chlorine and chlorinating chemicals" subforum, then open the second sticky for the Best Guess Chart.

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    Default Re: Using Bleach in the Pool

    I have drops and use them for the chlorine, ph, etc. But not CYA, because the test kit is missing a piece. Also, it is probably not the best kit (pool time), and it is probably old. I will replace on Monday. In the mean time, I will test again tonight, which will be 24 hrs after last test. I am grateful for your help. Thank you.

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    Default Re: Using Bleach in the Pool

    I will also test in the morning, and compare to the evening test. Thank you.

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    Default Re: Using Bleach in the Pool

    If you don't lose any chlorine, then you just need to filter out the dead algae. However, if your guesstimate of a CYA at 150 is anywhere close to accurate, it won't be long before you do have algae growing--in a pool with CYA over 100, you need to be keeping your chlorine at a minimum of 8 ppm--normal operating range for you would be 8-15 ppm, with a shock level of 25 ppm. In a 25K gallon pool, each half-gallon of 6% bleach will raise your chlorine level by 1.2 ppm, just to give you an idea....if your chlorine is now at 3 ppm, then to get to 8 ppm you would need to add 2.1 gallons of 6% bleach.

    That's why your CYA level is so critical--it determines how high you have to keep the chlorine in order to keep the pool clear and clean.

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    Default Re: Using Bleach in the Pool

    Well, I tested it tonight and the chlorine was down to 2 the ph was down to 7.4 (according to the drops) and the stabilizer on the test strip dropped to the appx 100 reading on the strip. This is 24 hrs after I put 3 gallons of bleach in the pool (6%). For that matter, I put 3 gallons in the night before too. Should I wait to test in the morning to see where I am at or add more bleach just to be safe?

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    Default Re: Using Bleach in the Pool

    The idea behind testing to see if you have a chlorine demand is that chlorine is consumed by two things: sunlight and pool goo. You can't really judge by looking at a 24 hour chlorine consumption whether you still have algae, because you don't know how much of the chlorine was consumed by the sun and how much by the goo. That's why you need to test at sundown after the sun is off the pool and again in the morning before the sun hits the pool if you're trying to establish whether your algae is all dead. You are always going to lose some chlorine during the day, due to the sun.

    With a CYA at 100, you still need to keep your chlorine at a minimum of 8 ppm, otherwise you're inviting algae to start. You'll need to look at your results taken at night and in the morning to determine whether you still have an algae problem or just dead algae that needs to be filtered out.

    If your chlorine is at 2, you need to add more bleach to get up to at least 8 ppm--but if you determine that you still have overnight chlorine consumption, then you need to shock it up to 25 ppm.

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    Default Re: Using Bleach in the Pool

    Tested tonight (had to go away for the w/e). It was 2 for chlorine. 7.4 for ph and the CYA was over a hundred. I had to use an old tube for the CYA test and the reading #s only went up to 100. I am guessing it was over 120 based on the spacing of the lines, but it is a guess. I will test again in the morning.

    I have 9 gallons of 6% bleach waiting to go in the pool if necessary and can get more. The pool is slowly, very slowly, clearing (1.5 weeks after initial shock treatments), but is still cloudy, especially in deep end. No new algae has popped up. I can still see dead algae on the bottom.

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