Well I added the 4oz of CYA then it rained for days and I had to empty about 12" out of the pool. I waited a full week to recheck CYA and low and behold it had dropped to about 25. So Tuesday I added 9oz of CYA and will retest next Tuesday. Wednesday the ph was really low, so I'm guessing the cya is doing its thing. No new chlorine consumption data valid since that week was nothing but rain and overcast. This week hopefully will be hot and rain free so we can start to get some results with increased validity.
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- Thread starter dsilchenstedt
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One thing that could be the cause of huge FC loss is that I think the CYA stabilizes the FC against UV loss as long as you are within recommended FC range. If you add excess chlorine then the stabilizer doesn't protect as well and you will lose the excess FC very quickly in a high UV environment. Someone like chemgeek with "advanced" chemistry knowledge would need to verify and even if I'm correct it still may be excessive loss.
I've been bringing my CYA up from 20 and it's at around 30 now and I have lots of sun exposure and only lose around 3 ppm FC a day at most.
I've been bringing my CYA up from 20 and it's at around 30 now and I have lots of sun exposure and only lose around 3 ppm FC a day at most.
That makes sense. I don't know if you are chemically correct but it sounds right
. I 'feel' like my FC has been more controlled lately but I have a lot of variable right now; rain, cloud cover, Lowered my target FC to 7 or 8, and increasing my cya to hit around 50. I have been bringing my FC up to 7 or 8 each evening and by the next evening it is between 3 and 5. Hope fully over the next week or two I will have results with a greater degree of validity. What you said sounds like it could very well be true and maybe part of my passed issue, thanks for the comment.I read some of Chem Geek (Richard's) posts and now my eyes are crossed but I do believe he states that the suggested range of FC to CYA puts them in equilibrium so going over that level will allow more unbound FC's thus they won't be protected from the UV. Unless Chem Geek or someone else with a greater grasp then me can correct this idea I believe that the shock levels allows a quick kill of algae and bacteria at the cost of losing FC faster then if you kept the FC closer to target levels. If you have algae and don't increase the FC above target maintenance level then the algae could grow faster then the available FC can kill it. (I don't think the name of what really disinfects is FC but rather Hypochlorous acid (HOCl) but like I said my eyes get crossed with this.)
That said, I'm still going with the assumption that high FC to CYA in the shock range will allow an increase in UV breakdown of the FC.
Glad your pool is clear and that your FC loss has dropped
That said, I'm still going with the assumption that high FC to CYA in the shock range will allow an increase in UV breakdown of the FC.
Glad your pool is clear and that your FC loss has dropped
What you said makes complete sense and feels like an obvious thing once you said it. I'll have to go read some of chemgeeks post, when I get a little free time. Thanks again, you just expanded my knowledge base.
Richard (chem geek) has all the technical issues covered. What salted is talking about is basically correct. Once you go substantially above the amount of FC your CYA is "protecting" it,is fair game and that additional FC gets consumed by UV relatively quickly.
Do you test after you add chlorine at night. Is it possible the bleach is degraded or you have your pool volume wrong.
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The unbound chlorine breaks down in sunlight much, much faster than the chlorine bound to CYA. Also, hypochlorite ion breaks down much faster than hypochlorous acid. That means that doing a SLAM tends to have large losses of chlorine in sunlight because 1) the active chlorine is nearly 10 times higher than the minimum FC level and 2) the pH tends to be high in a SLAM (especially if you didn't lower the pH first).
If there were no CYA in the water and the pH were high, one could lose half the FC every half-hour or so. Even with CYA, at a pH of 8.0 and a SLAM level of chlorine there is 0.86 ppm of hypochlorite ion in the water and that will degrade by half every 20 minutes. So even if you were maintaining the FC level, that's 2.6 ppm FC per hour. So you can see that one can easily have large chlorine losses during a SLAM, especially if they didn't lower the pH significantly before the SLAM.
If there were no CYA in the water and the pH were high, one could lose half the FC every half-hour or so. Even with CYA, at a pH of 8.0 and a SLAM level of chlorine there is 0.86 ppm of hypochlorite ion in the water and that will degrade by half every 20 minutes. So even if you were maintaining the FC level, that's 2.6 ppm FC per hour. So you can see that one can easily have large chlorine losses during a SLAM, especially if they didn't lower the pH significantly before the SLAM.
So my CYA is now at about 50 and I'm considering adding about four more oz by volume to bring it closer to 60. I've been losing about 4ppm/day this past week. So things are looking better; I take it to 7 and 24hrs later it's sitting around 3ppm. Been adding about 15oz of 10%/day. This is sounding more right but a little more CYA would probably do me good.
15 fluid ounces of 10% per day in your 3800 gallon pool would be 3 ppm FC. Anyway, you can certainly increase the CYA to see if it reduces your daily chlorine usage. If you suspect the loss may be more than sunlight, you can do an overnight chlorine loss test. If you do that at normal chlorine levels, you should find the loss to be very low at no more than 0.5 ppm.