smallpooldad said:
I realize that you and others are strongly in favor of higher CyA levels of 70 to 80 ppm and this paper that you cited from 1993 finds no issues but as I stated I would personally be happier with more research, or as I stated "enough" maybe 10 - 20 papers or so. I will therefore continue to keep it in the 30 - 35 ppm area.
You can obviously do what you want, but it isn't just that one study. The
US EPA Robust Summaries for Trichloro-s-triazinetrione prepared in 2004 also lists numerous detailed toxicity and irritation studies for cyanuric acid and sodium cyanurate (pages upon pages upon pages of data and studies) as well as Trichlor (which of course is toxic to fish at lower levels due to the chlorine, not the CYA, so look specifically for the "Identity" of either cyanuric acid or monosodium cyanurate). Cyanuric Acid, and its relative monosodium isocyanurate, is studied far more than most chemicals so I am really puzzled as to why you picked this particular chemical to be concerned about over all others. In that EPA report, I counted 32 unique studies for CYA or cyanurate. As I said, there are many other chemicals with far greater risk, if you were going to go down the path of worrying about specific chemicals. I can try to be polite about this, but I cannot emphasize enough how wrong you are with this particular chemical being any sort of issue with regards to health at the level used in pools.
smallpooldad said:
There is also the often discussed issue of the CYA/Chlorine sanitation relationship much discussed in the "Deep End" where the verdict it seems to me, and I may indeed be wrong, is still out, so I feel while in some peoples' minds I may be "way,way off base" my own opinion is that I have not yet constructed a "base" in my mind and am open to further studies.
The verdict is not still out and has never really been out. That topic was in The Deep End not because of its controversy, but because it was technical. The results of the chlorine/CYA relationship are in the
Chlorine / CYA Chart in the Pool School which is a key foundation for maintaining a sanitary pool free of algae, initially figured out by Ben Powell of
The PoolForum (and
PoolSolutions) and later worked on via the chemistry by myself and others. The "Chlorine / CYA Relationship" section in the
Certified Pool Operator (CPO) training -- What is not taught thread has numerous references to peer-reviewed scientific papers that not only determined the specific chemistry involved, but validated it in terms of kill rates for pathogens, rates of oxidation of organics, ORP levels, etc., not to mention the tens of thousands of pool owners who maintain their pools using this relationship to minimize problems. The only controversy is a made-up one from some chemical manufacturers who claim that high CYA levels don't matter (at the same FC level) in order to promote their stabilized chlorine (e.g. Trichlor, Dichlor) sales.
smallpooldad said:
Adding borates might make the alkalinity more stable so I presume I could raise the alkalinity and it might stay there without dropping too quickly this would negate the usage of raising the calcium, as to acid usage I am unsure, perhaps I am not understanding this correctly.
Even if you were to use the borates, which you won't because of your dog that I presume drinks from the pool every day, you would not raise your TA level (beyond that naturally raised by a higher CYA level). The lower TA helps stabilize the pH by slowing down the rate of pH rise due to carbon dioxide outgassing. Though the Borates additionally buffer the pH, there is no good reason to raise the TA which would only worsen the problem causing you to need more acid to compensate for pH, though perhaps only needing to add it less frequently due to the Borates (but the total acid over time would probably still be about the same).
smallpooldad said:
I hope you can see from my perspective why I and perhaps other pool persons, especially public pool operators still cling to the lower CyA levels.
The commercial/public pool segment uses a lower CYA level because they do not need a higher CYA in most cases because most of the chlorine consumption is from high bather load. Anything above around 30 ppm CYA doesn't have an apparent effect on chlorine savings, but that is not the case for a residential pool since low bather load outdoor pools have most of their chlorine loss come from sunlight. CYA protects chlorine from that UV degradation. Commercial/public pool operators also want to use a lower CYA just in case they need to super-chlorinate the pool if there is a fecal diarrhea accident or a known Cyrptosporidium outbreak. That is not an issue in residential pools -- not one such Crypto incident in any of the residential pools or spas on any pool/spa forum I have seen.
smallpooldad said:
On the other hand if I was to go ahead and forget the torpedoes and attorneys, which I might yet do, what might you change in the following proposed setup:
10,000 gals
FC 8.0
ph 7.6 (5 ozs Jack's Magic "The Purple Stuff weekly - works well and as advertised, however Jack said to keep it in the 7.2 -7.4 area)
TA 80
CH 375
CyA 70
Salt 3300
Temp 78 F (can go down to 72 F if weather is overcast, and/or I turn off the heat pump pool heater)
CSI -0.19 (from Pool Calculator)
PoolPilot SC-60 cell at Power Level 2, production percentage as yet unknown, runtime 5 hours. Could I keep up with level of FC 8? Or is 8 too high, I note in "PoolEquations" this would give me an HOCL of 0.48 slightly below the 0.50.
As I noted earlier, I would NOT raise the TA level to 80. You have found reasonable pH stability at the lower TA and I wouldn't change that by more than what the CYA would naturally add to TA. So you could just modify what you have to get:
FC minimum of 4 ppm (or somewhat higher if you want to prevent heartier algae, but normally no need to go more than 8 ppm, but read below)
pH 7.4 (for Jack's, if that is what they require)
TA 65
CH 900
CYA 80
Salt 3300
Temp 78ºF (is that normal during the summer as well?)
The carbonate alkalinity, which is the TA minus that contributed by CYA, is still at 40 ppm as before. If you add CYA, the TA will automatically rise, but the amount we care about for carbon dioxide outgassing and the CSI will remain the same. The CSI for the above is also at around -0.2 so similar to before. Note that I am assuming that your pool is in full sun for a good portion of the day. If it is not, then raising the CYA level won't help as much.
smallpooldad said:
My only concern would be the high chlorine number which might create a big fight between rising pH and acid. Our UV index is very high as our latitude is North 21 degrees, from experience algae will quickly pop up if the chlorine level is held at too ambitious a level say 3.5 at the present numbers, so I prefer more conservative (higher levels).
You are assuming that the loss of chlorine is based solely on the FC level, but that is not true. The rate of loss even in absolute FC terms is lower when the CYA level is higher even at the same FC/CYA ratio (that is, even when the FC is proportionally higher). This was shown in experiments done by Mark on this forum (see
this post) and has proven out in others' real pools as well. I'm not sure why you have your FC level at 5 ppm with your CYA of 30 ppm. Why is it that high? This is over 3 times higher than needed in an SWG pool and over twice as high as the minimum in a manually dosed pool. You say that your experience is that algae will develop if not kept at a higher level, but are you sure that happens with an FC of 3 and a CYA of 30 ppm? I suspect that some reading may be off. Either that or you've got a particularly hearty form of algae (do you get yellow/mustard algae?). If that is the case, then perhaps a CYA of 80 ppm won't be so good since you would proportionately need an FC of around 10-11 ppm to be the same as where you are today. You could start out by going to a CYA of 50 ppm with an FC of 6.6 ppm and see how that goes, even lowering the FC somewhat to see if you can still keep algae away at a lower FC/CYA ratio.
Richard
I was just trying to let him know what the "accepted" CH levels are in a properly balanced pool. He stated that he has very soft water, so it seems odd to me that he would deliberately try to raise CH (especially when so many are trying to lower it!). Given his soft water, it seems he should stay within all of the approved parameters for pool water.