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Thread: The fine art of CYA reading

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    spylab's Avatar
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    Jun 2014
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    The fine art of CYA reading

    When testing CYA level, do you take the reading when you can no longer see a defined dot at the bottom of the test tube or when you can't see any hint of grey at the bottom? Does it matter if you look away and look back again? (I know that sounds funny but sometimes I think I can't see it anymore and my eyes feel fuzzy and when I look back I see the dot again)

    I'm in TX and we have had extreme rainfall this year and I ended up with extreme algae. I started treatment about 5 days ago adding bleach and I added "pool conditioner" that came with my pool to raise the CYA because it was low in the initial test. I ended up with CYA around 70 to 80 but not sure how accurate because I had also added lots of bleach. My water turned a milky white the next day and it started raining again. (We have been in extreme drought for a few years and as soon as I have a pool we are getting record rainfall and flooding)

    My water was remaining milky and last night my clarifier finally arrived and I hoped to wake to a clear pool. Last night I had a FC of 23 and CC 0.5.

    This morning I can see the bottom of the pool but the water is still cloudy. I could also see a little bit of algae left over on the bottom which easily stirs up with the brush.
    This morning the FC is 18, CC 1.0, CYA 50-60, PH 7.5, TA 100, CH 300, Salt 3400. (After taking the water sample this morning I dumped a gallon of bleach in which is about twice as much as I should have according to pool math- I think I was angry at being able to see algae again LOL)

    I want to be sure about exactly when to read the CYA level so I know an accurate FC level for the SLAM.

    I added the clarifier about 12 hours ago at double the dose rate as allowed for extra cloudy pools. How long before I can add more?
    I am beginning the think there is no chance of swimming tomorrow either
    5,400 gal, AG PVC coated kevlar like scrim liner, Advantage 1.5 HP with 19" Sand Tank
    Krystal Clear Ozone & Salt Water System, Taylor TF-100 and K1766 Salt Test

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    Re: The fine art of CYA reading

    It's when you no longer see a defined dot. This link from Taylor shows the dot pretty well obscured. See also this post of mine that shows a 50 ppm standard solution at the 50 ppm line where it's pretty obscured and then at 60 ppm where it is slightly visible and 70 ppm where it is more visible.

    We do not normally recommend the use of clarifiers because they don't always work, you make things worse if you overdose, and they are usually not necessary since proper filtration and use of chlorine can usually clear a pool. For finer filtration from a sand filter you can Add DE to a Sand Filter, but do not do that if you've already added clarifier (it sounds like you already did, unfortunately) since clarifiers and use of DE are incompatible (DE filters too finely and clarifiers will just gum up DE).

    Why did you add a clarifier? Perhaps we need to make that more clear in the Pool School that you should not, in general, use clarifiers or flocculants.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    spylab's Avatar
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    Jun 2014
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    Re: The fine art of CYA reading

    Thank you so much for those links! That is very helpful.

    I added the flocculant because I had seen them mentioned somewhere on here with the drawback being mainly cost and the fact that my pool was going nowhere for 3+ days with the filter running 24 hrs/day. I do not have a pressure gauge on my sand filter and no place to add one that I know of. I did backwash every day until clear but had no clearing of water until I added the flocculant. Thanks for the tip to not add DE now that I put the flocculant in!

    With just one jet in a rectangular pool I suspect my circulation is not the best. I ordered a rotating cleaner jet that is supposed to markedly improve circulation but it may be another week before it arrives.

    Just tested again FC is 33.5 and CC is 1.0.

    Thanks again for your assistance!
    Last edited by spylab; 07-11-2015 at 11:11 AM. Reason: additional information
    5,400 gal, AG PVC coated kevlar like scrim liner, Advantage 1.5 HP with 19" Sand Tank
    Krystal Clear Ozone & Salt Water System, Taylor TF-100 and K1766 Salt Test

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