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Thread: Chemically Remove CYA

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    In the Industry

    Join Date
    Aug 2012

    Chemically Remove CYA

    Hi guys, I am a pool professional(serviceman) from the Boston area, and completely new to these threads. I have seen many strange things over my years in the industry, and finally want some answers! So I have read through some of these and other threads, and it seems to be pretty much agreed that the only way to lower CYA is by drain/refill. There seems to be an old rumor about ammonia, but that has been debunked. Well, I have serviced a high end gunite pool on the ocean for about 4 years now, and something strange recently happened. On Thursday, the pool was looking great and everything tested within normal ranges. By Monday (I service it twice a week), it was a complete swamp. It is salt water pool, with CYA around 70 and FC around 4 on Thursday. On Monday, FC was 0, and so was CYA! After a little investigation, I found fertilizer pellets around the pool area - they had their lawn treated, and it rained over the weekend. It did introduce low levels of phosphates, as expected. I brought the pellets to a landscape/nursery place that I share a parking lot with. They told me it was a product called Weed and Feed, made by Scotts I think. I wasn't surprised this dropped out the FC and added phosphates, but to completely neutralize the CYA? As far as I can tell, there is a chemical in that product that can lower CYA. So this leads me to believe that CYA CAN be lowered other than drain/refill, which would help when I come across too high levels and people don't want to spend money on water. Any insight would be appreciated! Also, stay tuned for some of my upcoming posts about other strange situations I have encountered.

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    duraleigh's Avatar
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    Apr 2007
    Sebring, Florida

    Re: Chemically Remove CYA

    Welcome to the forum. Do you think you can duplicate that result?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Mod Squad Bama Rambler's Avatar
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    Jun 2009
    SouthWest Alabama

    Re: Chemically Remove CYA

    There was a product marketed several years ago to remove CYA but it caused problems. Richard (Chem Geek) mentioned it in a topic or two. It may have been the same chemical that's in the Weed & Feed.

    Of course it could be soil bacteria getting in the pool and converting the CYA to ammonia.
    Dave J. TFP Moderator
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    Re: Chemically Remove CYA

    Currently, I am having a serious issue with too much CYA and am trying to reduce it by draining the water. I won't Hy-jack the thread with my problem, but will say that I did in fact get Scotts weed & Feed into my pool by accident about a month ago and had it cloud up on me. After reading several threads, I shocked it for a week trying to clear it back up. The CYA never dropped.

    Now I'm more careful about fertilizing my lawn as it was a tremendous effort to clear the pool water up.

    It was crystal clear on Sunday. By Monday we couldn't see the drains.

    That was my experience with Scotts Weed & Feed.

    Maybe, I should get a bucket of my pool water and add the Weed & Feed to see if it drops. Obviously, I will have introduced a phosphorous problem to the water by doing so.

    Once again, I think it might just be easier and safer to just drain the water and refill. I don't think if would be a healthy decision to adjust with fertilizer.
    Someone once said "No man drowns if he perseveres in praying to God, and can swim."

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    Swampwoman's Avatar
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    Apr 2012
    Grand Rapids, MI

    Re: Chemically Remove CYA

    The cya in my foreclosure pool was zero on opening, and the swamp smelled strongly of ammonia and sulfur. Bacteria can eat cya -- this has been documented -- but seems weird in such a short interval. So while the blow in of the weed and feed may have exacerbated the situation, maybe it also gave nutrient to the the of bacteria that eats cya
    In other words, maybe it wasn't the fertilizer, but WHAT it fertilized!
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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Chemically Remove CYA

    It was likely to be CYA degradation by bacteria this post. The fertilizer just added ammonia to the pool that used up the chlorine quickly so when it got to zero and with plenty of nutrients (ammonia and phosphates) in the pool, both algae and bacteria could grow prolifically. The bacteria then proceeded to use the CYA as a delicious nutritious nitrogen food source converting it into ammonia or, depending on the bacteria, nitrite, nitrate or nitrogen gas.

    As I describe in the thread It Can Happen to Anyone - Zero Chlorine, CYA-->Ammonia, the consumption of CYA by bacteria can happen very quickly in a matter of days. Unfortunately this process is not readily controllable and if it results in ammonia then the resulting chlorine demand is huge and can be expensive.
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