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Thread: Is it common to have a reduction of CYA over time?

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    Is it common to have a reduction of CYA over time?

    Here's current results:

    ph. 7.2
    cya 30
    calcium hardness 220
    alkalinity 100
    fc 4.5
    cc 0

    I've noticed over the last month that the CYA number has dropped some (from 45ppm to current 30ppm). We did have more use and splashing over the last few weeks and I did a leak test on the pool before putting into service so no other water loss. Is there some natural deterioration of CYA that occurs over time?
    18,000 gunite pool/spa combo. Pebble tec, iaqualink rs8, cl580 filter, aquapure 1400, 400k btu lx heater, 10 solar panels, jandy 1hp, 1 1/2hp, and 2hp stealth pumps for circ, spa, waterfall

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    needsajet's Avatar
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    Re: Is it common to have a reduction of CYA over time?

    Main sources of the CYA drop during swimming season include rainfall if water overflows or needs to be drained. Splashout as you mentioned and water drained due to backwashing (although not a factor for you) also take CYA with the water. There is degradation caused by the chlorine, although it's fairly slow. CYA degradation caused by chlorine is faster if water is warmer. When a pool has no chlorine for a period of time, bacteria can grow which consume CYA, but I'm only mentioning it for completeness.

    Unrelated, but I noticed that you water is a bit aggressive, and if it were my pool, I'd keep pH at 7.5 and above.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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    Re: Is it common to have a reduction of CYA over time?

    Quote Originally Posted by Rossterman View Post
    Here's current results:

    ph. 7.2
    cya 30
    calcium hardness 220
    alkalinity 100
    fc 4.5
    cc 0

    I've noticed over the last month that the calcium number has dropped some (from 45ppm to current 30ppm). We did have more use and splashing over the last few weeks and I did a leak test on the pool before putting into service so no other water loss. Is there some natural deterioration of CYA that occurs over time?
    there's an article somewhere on the site written by chem_geek indicating slow CYA degradation from FC. We're talking here about months in time scale, very slow process.
    44k plaster pool, Pentair 011018 pump, DE6020 filter, LED lights, K2006 test kit

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    Re: Is it common to have a reduction of CYA over time?

    Quote Originally Posted by needsajet View Post
    Main sources of the CYA drop during swimming season include rainfall if water overflows or needs to be drained. Splashout as you mentioned and water drained due to backwashing (although not a factor for you) also take CYA with the water. There is degradation caused by the chlorine, although it's fairly slow. CYA degradation caused by chlorine is faster if water is warmer. When a pool has no chlorine for a period of time, bacteria can grow which consume CYA, but I'm only mentioning it for completeness.

    Unrelated, but I noticed that you water is a bit aggressive, and if it were my pool, I'd keep pH at 7.5 and above.
    yes- back from a week of vacation and ph was pretty high from SWG. A little to generous on the acid today ��
    18,000 gunite pool/spa combo. Pebble tec, iaqualink rs8, cl580 filter, aquapure 1400, 400k btu lx heater, 10 solar panels, jandy 1hp, 1 1/2hp, and 2hp stealth pumps for circ, spa, waterfall

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    needsajet's Avatar
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    Re: Is it common to have a reduction of CYA over time?

    Excellent. So time to add some CYA I guess. Go swimming; sounding excellent from sunny-but-60 Sydney

    - - - Updated - - -

    If you're above .08, don't click this link: Degradation of Cyanuric Acid (CYA))
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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    Re: Is it common to have a reduction of CYA over time?

    Most common loss of CYA is caused by splash out, a leak, or backwashing. I'm a pool service professional (I know my profession is hated here and my advice/experience will probably fall on deaf ears) and have had to constantly battle outrageous CYA levels due to the use of trichlor tablets and customers extreme fear of ever draining their pool. To lower CYA at my most problematic pools I simply fill the pool as close to the top as possible and the swimmers do the rest. One commercial pool this year had a CYA reading of 300ppm in May. I insisted they drain the pool with no luck. I set the autifill to keep water 2 inches from the top and the resulting splash out over the summer has resulted in CYA of 40ppm. Be thankful that your CYA is low, it's very cheap and easy to raise and very difficult to lower without draining.

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    Re: Is it common to have a reduction of CYA over time?

    Quote Originally Posted by buytheseapools View Post
    ... I'm a pool service professional (I know my profession is hated here and my advice/experience will probably fall on deaf ears) ...
    I don't have this impression and I believe you'll find input from several pool professionals at the beginning of this forum. Besides the rest of your post matches 100% to what this forum promotes.
    44k plaster pool, Pentair 011018 pump, DE6020 filter, LED lights, K2006 test kit

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    Re: Is it common to have a reduction of CYA over time?

    Why is a pH of 7.2 too agressive? I don't have a PhD in chemistry but isn't it true that chlorine is 4Xs more effective at a 7.2 pH than it is at 7.8 pH? I might be wrong here again, but I beleive the Germans invented water chemistry and they recommend pH valves between 6.8 and 7.2. How is it possible for nuetral or slightly basic water to cause damage to equipment, pool finish or skin? When pH exceeds 8.3 the chance calcium scale and copper turning swimmers hair green becomes a real problem. I'm only on this site to continue my education, so any and all replys are helpful.P.S. Sorry about your womens soccer team, what a heartbreaker.

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    needsajet's Avatar
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    Re: Is it common to have a reduction of CYA over time?

    Very exciting for Brazil I suppose, but yep, didn't go our way today.

    Pool experience is valued here and questions are most welcome, provided we keep the thread on point for the OP.

    Raising the pH on this pool from 7.2 to 7.5 will help assure maximum plaster life, per the calcite saturation index. The index can be ignored by staying within our recommended ranges for water chemistry, found here: Pool School - Recommended Levels

    You'll learn that the goal here is maximum availability of safe and sparkly clean residential pools, along with optimized annual cost. Glad to hear you're up to speed on the FC/CYA relationship.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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