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Thread: CYA test still showing high after draining 70% of the pool

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    CYA test still showing high after draining 70% of the pool

    Hi Guys!

    Had a pool for not too long now and still trying to figure out proper chemical/cleaning procedures. My calcium hardness and CYA was way too high so I ended up draining 70% of the pool. The CYA was reporting a little bit above 100 and the Calcium hardness was reporting somewhere around 500.

    After draining the pool aboput 70% and taking it to the pool store for testing again the results are:
    TA: 140
    PH: 7.7
    CH 268
    FC: 0
    CYA: 132

    I don't get it. It's like the CYA went up. I recall it being lower then when i drained the pool. Maybe the CYA was just so high that the test kit couldn't read it properly and I really just needed to drain the whole pool?

    - - - Updated - - -

    Also, it sounds like i should be using liquid bleach (bought from the grocery store) to prevent the CYA from getting any higher?

    - - - Updated - - -

    Also, it sounds like i should be using liquid bleach (bought from the grocery store) to prevent the CYA from getting any higher?
    25,000 Gallon Pool, In Ground, Plaster, DE Filter (need to get model), need to get pump, pool build year unknown

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    Richard320's Avatar
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    Re: CYA test still showing high after draining 70% of the pool

    I wouldn't trust pool store results. You need your own kit if you want to stop being jerked around and told to buy this, then that, and then some oither thing, then more of this, and more of that, and add this product, and now look, you've added too much stuff, your total dissolved solids are too high, you need to drain.

    Here's another thread from someone with the same problem. Check my reply there, so I don't have to type so much.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: CYA test still showing high after draining 70% of the pool

    Anytime the CYA is at or north of 100, the pool store is not going to be able to give you an accurate test number. In fact, over 100 it's pretty difficult to get the test right on your own, although you can get pretty close by diluting pool water with tap water 50/50 then doubling the result.

    So let's say your CYA is 300. The test is going to show around 100. Then you drain half, which puts your CYA at 150. The test will still show around 100. But if you dilute 50/50, you should get 75, which then doubled will give you the accurate(ish) 150.
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    Re: CYA test still showing high after draining 70% of the pool

    1. Pool stores are notorious for inaccurate cya tests. For example, for months, leslies was telling me mine was 40. When I got my own test kit and results I found it to be actually north of 340ppm. It took draining and refilling 40,000 gallons to correct it; just a little over 70%
    2. bleach doesn't lower or keep cya from getting higher, but yes you'll want to use at least 8.25% bleach to chlorinate you pool. I suggest walmarts great value as they turn it over quickly so it's always fresh!
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    Re: CYA test still showing high after draining 70% of the pool

    cool. Thanks! The answers it. Guess i shoulda drained the whole thing! Now i guess I should go back and drain it again dangit!
    25,000 Gallon Pool, In Ground, Plaster, DE Filter (need to get model), need to get pump, pool build year unknown

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    Mod Squad jblizzle's Avatar
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    Re: CYA test still showing high after draining 70% of the pool

    And order one of the Recommended Test Kits
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    Re: CYA test still showing high after draining 70% of the pool

    Based on my recent experience i would really get a good test kit and test yourself before draining any further. I did my drain based on the results from the pool store. When my test kit arrived I found out their results were way off and I had actually drained too much. I am temporarily using my leftover trichlor pucks to raise it back up slightly.
    19,000 gal aqua blue pebble sheen, 3.5-7 ft. depth, chiseled flagstone coping, spillover spa, raised back wall with stacked stone face including two columns and curved wall water feature with three 18" sheer descents, two bubblers on 5' x 10' suntanning shelf, Pentair IntelliFlo Variable Speed, Pentair FNS Plus 60 sq ft DE filter, Pentair Mastertemp 400K BTU, Pentair Legend, Rainbow 320 chlorinator (now unused), K-2006 test kit.

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    Re: CYA test still showing high after draining 70% of the pool

    I went back to the test kit i have, and for the sample, I removed 60% of the sample water, and replaced it with tap water. Then I retested for CYA and it was around 45. So i guess i need to go back and drain another 70% of the water.
    25,000 Gallon Pool, In Ground, Plaster, DE Filter (need to get model), need to get pump, pool build year unknown

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    Re: CYA test still showing high after draining 70% of the pool

    I'm not sure about your math. It seems like that would give you a CYA close to 30 ppm.....not bad but I would suggest 50 ppm in TX.

    Not sure why you diluted to a 60/40 sample ratio.......50/50 would've been easier to calc.
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    Re: CYA test still showing high after draining 70% of the pool

    What kind of test kit do you have? And why 60%
    Pool size: 24000gal inground Vinyl-Taylor k-2006 and k-1766 test kits and-speed stir
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    Mod Squad jblizzle's Avatar
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    Re: CYA test still showing high after draining 70% of the pool

    Have you stated which test kit you are using? Hopefully not strips.
    Jason, TFP Moderator
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    Re: CYA test still showing high after draining 70% of the pool

    My test kit is the Taylor K-2006C.

    I mostly did a guess that since the CYA was at ~130 (according to the pool supply store), i'd probably need to replace more then 50% to get the CYA down to a suitable level. Since the test kit is based on 7ml pool water i chose to use 2ml of pool water and 5ml tap water for the test. I guess that's actually replacing ~70% of the sample with tap water ( i must have fudged something).


    Is there a reference on what you should keep the CYA at? I just assumed it was 40 based on the pool calculator. So it depends on the climate? So texas' optimum level is ~50ppm.
    25,000 Gallon Pool, In Ground, Plaster, DE Filter (need to get model), need to get pump, pool build year unknown

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    Mod Squad jblizzle's Avatar
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    Re: CYA test still showing high after draining 70% of the pool

    I would start between 40 and 50ppm and see how the FC consumption is.
    Jason, TFP Moderator
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    Re: CYA test still showing high after draining 70% of the pool

    Quote Originally Posted by HopelessLee View Post
    Since the test kit is based on 7ml pool water i chose to use 2ml of pool water and 5ml tap water for the test.
    That's not 60/40. That's 71.5/28.5. Not that you're really that accurate, because the more you dilute the more you increase your error, because small changes in the 2 ml of pool water lead to bigger changes in your result. If your guess is 130 ppm, then a 50/50 mix will give you more accurate results. Even if it is closer to 160 (the number I computed from your measurements) you will still be within the range of the test.

    Your CYA must have been insanely high before. I'm guessing the pool store had you using lots of trichlor (pucks) and dichlor (shock).
    20,000 gal in-ground plaster pool with sand filter. Replastered recently. Mostly adding bleach and acid. CYA was high when I took over.

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    Casey's Avatar
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    Re: CYA test still showing high after draining 70% of the pool

    All I have to say is your CYA must have been astronomical!
    I'd bet you my bikini you'll never get TFP water from a pool store!

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