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Thread: CYA and Ph level

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    kdubya815's Avatar
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    CYA and Ph level

    Hello! I am trying to open my pool (a little late, I know!!) and I tested my water. My CYA was 120 ppm. I know the only way to lower it is to replace a portion of the water. My question is this: I live in middle TN, and we just had the major flooding in our area. When I tested the water, the ph was 8.7. I assume that this high ph level can be contributed to the rain water because my ph has never been that high. During the process of replacing some water to correct the CYA level, will this also help with lowering the ph? I tested my tap water (which is what I will replace the water with) and it was 6.8. Should I wait to adjust the ph until after I have corrected the CYA problem?


    Also, I believe I remember learning that you should adjust your TA, Ph, and CYA BEFORE you shock. Is this true or is this something I dreamed up??

    Thanks for any help you can provide!!
    18x36 Grecian style vinyl 23,000 gal inground pool, Hayward Pro Series S220T sand filter, Hayward Super Pump 1 hp.

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    Mod Squad JohnT's Avatar
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    Re: CYA and Ph level

    It's hard to accurately measure pH when you are at shock chlorine levels, so it's best to do anything which requires pH changes prior to shocking.

    TA isn't something that usually needs to be adjusted in a hurry, so it's usually better to worry about it after shocking so you can deal with the problem that caused you to need to shock first.

    The CYA test isn't linear, so a result of 120 could really be 150ppm or more. The only way you'll know is when you do the water change. You can approximate the results by diluting your pool water sample with tap water and the doing the CYA test using the mixture. 50% pool water and 50% tap water should test at half the CYA level your pool currently has, but measuring accuracy and the poor resolution on the CYA test make it useful only as an approximation.

    As to the effects of a water change on pH, we'd need your full test results for both your pool water and tap water to make an educated guess. Particularly TA.
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    Re: CYA and Ph level

    What did you use to test your pH? Did you use an electronic tester?

    Unless somebody else thinks differently, I think that you should probably go ahead and change out water as that will lower your CYA and your pH both. The problem is that since you have had so much rain, I worry about draining too much and floating your pool. You may need to drain and fill simultaneously. This will take a lot more water than it would if you simply drained first and then refilled, but then you don't have to worry about floating the pool.
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    Re: CYA and Ph level

    I agree with Mag- with the recent rain you don't want to drain too much as your liner will likely float. I would go down to the bottom of the skimmer, refill, recirculate and repeat 2 or 3 times and then retest the CYA level.

    Once you get your CYA level down you can retest for the PH and readjust it into range (up or down, whichever it needs after all the water replacement.)

    First, CYA
    Second, PH
    Third, TA...if necessary
    fourth - shock... if necessary
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    Re: CYA and Ph level

    Thanks for all your advice! I am draining and refilling right now. Since I do not have a test kit yet (will order one asap), I took it to my local pool store for them to test it. I do believe it was an electronic tester. They tried to sell me several chemicals, but thanks to tfp I was able to feel confident that I knew exactly what I needed to do to adjust my levels. I will retest it after I have done the drain/refill cycle about three times.

    One other question, the pool is very green and has a lot of leaves on the bottom. I have been scooping and scooping, getting most of it out. Could I go ahead and vacuum to waste to drain the pool down a little and get more of the gunk out? Trying to kill two birds with one stone...
    18x36 Grecian style vinyl 23,000 gal inground pool, Hayward Pro Series S220T sand filter, Hayward Super Pump 1 hp.

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    JasonLion's Avatar
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    Re: CYA and Ph level

    Yes, vacuuming to waste sounds like an excellent idea.
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    Re: CYA and Ph level

    Thanks for your help! I am going to try to get some pics now so I can have before/after pics. Hopefully, I will begin shocking Friday evening so I will have the weekend to check it constantly.
    18x36 Grecian style vinyl 23,000 gal inground pool, Hayward Pro Series S220T sand filter, Hayward Super Pump 1 hp.

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    kdubya815's Avatar
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    Re: CYA and Ph level

    Well, I have managed to get my CYA down to 80 and my ph down to 8.1. I am going to get some muriatic acid to lower the ph. I am very anxious to start shocking tonight. Can I begin the shocking process or do I need to get my CYA down a little (or a lot!) further before I do so? Of course, I don't want to pour $ down the drain, so I want to shock at the ideal time. Also, the pool store where I got my water tested recommended the "mustard algae treatment". I believe the chemical is sodium bromide. Would it be good to give this a try along with shocking? I am very hesitant about it, just from knowing what little I do know. Hopefully, some of you can give me your thoughts on this?!?!

    Also, I have vacuumed to waste a couple of times. The first time, I got a lot of leaves and mess (had to stop several times to clear the basket - it was so full all I could see was leaves!). The second time, the skimmer basket did not fill up near as fast with leaves (I stopped it twice to empty the basket and could actually still see the basket!!) Hopefully, this is a good sign!! My family would love to be swimming now, so I am very anxious to get this pool blue and clear!

    Thanks for your help!!
    18x36 Grecian style vinyl 23,000 gal inground pool, Hayward Pro Series S220T sand filter, Hayward Super Pump 1 hp.

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    Re: CYA and Ph level

    Lowering CYA further is a good idea. However, you can get by with a CYA level of 80 if you have to.

    It is important that you get the PH down before you start shocking. Lower PH to between 7.2 and 7.4.
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    Re: CYA and Ph level

    Suggestions:

    First, forget the mustard algae treatment

    Second, vac (to waste) and clean all visible organics from the pool before you try to start shocking the pool. They will just eat up the chlorine.

    Third, do yourself a big favor and lower your CYA to at least 50-ish. If you choose to leave your CYA level at 80, it is going to take a ton of liquid chlorine/bleach to shock your pool.
    This translates to $$.

    You can go to Jason's Pool Calculator (link in my sig) and calculate how much LC/bleach it will take to raise your pool (volume of gallons) to shock level with a CYA of 80 and then calculate how much it will take to raise it to shock level with maybe a CYA of 50.

    Good luck!
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    kdubya815's Avatar
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    Re: CYA and Ph level

    Okay....so I FINALLY was able to order my test kit tonight...I'm so excited and can't wait to use it! I was a little apprehensive about spending the $$, but from all the posts, it sounds like a great investment!

    On to the question...I am very ready to begin shocking. I drained/refilled 3 times, but the only way for me to really tell about the CYA level is to take it to the pool store (very rude most of the time - they look at me crazy when I don't heed their advice for all the expensive chemicals). However, I have read many posts stating that the pool store's numbers are not very reliable! So, I don't really want to go back. Last time I had it checked, it was around 80, and I vacuumed to waste one more time, then refilled it. That makes a total of 3 times of draining/refilling. Do you think I could go ahead and start shocking w/o knowing the exact CYA level?

    Also, we have rain again in the forecast (not good right after the flooding). Can I still go through the shocking process even though I know the rain may come? Will the rain affect my FC levels too drastically?

    Keeping all of this in mind, is it a good idea to start shocking now without the test kit (knowing the kit is on the way), or should I just wait until next weekend when I know I will have it? It is getting harder and harder for me to let the pool sit out there green while I really could be swimming now if the water was clear!! However, being sure that I am not throwing money down the drain is quite a bit more important to me than a few swimming days!

    Sorry for all of the questions, but I just find that I can get unbiased, straight to the point answers on this forum! You have made me feel like I can actually take control of my water so that I can ensure that my pool stays crystal clear without way too much effort and money! Thanks for any advice you can give.
    18x36 Grecian style vinyl 23,000 gal inground pool, Hayward Pro Series S220T sand filter, Hayward Super Pump 1 hp.

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    Re: CYA and Ph level

    To shock the pool, you need some idea of the CYA level and some way to measure the FC level, so you can know if you need to add more chlorine or not. We can guess at the CYA level, saying it is 60 is probably good enough for now. Do you have anything you can use to measure the chlorine level? Even a simple OTO test, drops turn the sample yellow, which is then compared to a color chart, would be enough to get started (though it will require some guess work).
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    kdubya815's Avatar
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    Re: CYA and Ph level

    I do have some older test strips that will test for FC. They are past the expiration date...is that really important? Can I still use them? I

    f not, I do have a basic drop test kit from WalMart, I just need to replenish the OTO solution.
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    JasonLion's Avatar
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    Re: CYA and Ph level

    Good. Since we are assuming that CYA is around 60, shock level is around 20. With an OTO test, that gives an orange color. If you are using the OTO test, measure the chlorine level about 20 minutes after your first dose of chlorine to get an idea of what the orange should look like. With the test strips, you will need to mix one part of pool water with an equal amount of chlorine free water (perhaps distilled water) and test that. You can use either of those to get a very approximate idea of the FC level. Because the tests are approximate, it is better to go a little too high, rather than risk being too low.
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