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Thread: Is there anthing wrong with high levels of calcium.

  1. #1
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    Is there anthing wrong with high levels of calcium.

    As the pool water has a tendency these days to even out at an alkalinity reading of 50 ppm (prior to the last year or so it use to go down to 60 -70 ppm), I decided to up the calcium to 900 ppm. This has lowered the usage of acid and kept the CSI within reasonable bounds. I did recently read that taking the calcium over 600 which was the number I used before I made the change may not be good for the pool, but nowhere can I find a reasoning for that remark.

    So far after two weeks at the 900 level the pool water seems to have no adverse consequences presenting themselves, and the acid usage is way down, and no need to add baking soda.

    Any thoughts, I just want to make sure I am not messing up anything.

    The pool numbers are as follows:

    10,000 gals

    FC 5.0
    CC 0
    TC 5.0
    ph 7.4 (To keep wind swept iron under control, also use 5 ozs Jack's Magic "The Purple Stuff weekly - works well and as advertised, Jack said to keep it in the 7.2 -7.4 area)
    TA 50 (was 70 by adding Baking Soda weekly)
    CH 900 (was 600)
    CyA 30 (I know some may disagree but it works fine for me with AutoPilot's PoolPilot SC-60 set at power level 2 at 36% for a 5 hour run)
    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 0.17 now, was 0.16

    Thank you to those that might help.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  2. #2
    Administrator JasonLion's Avatar
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    Re: Is there anthing wrong with high levels of calcium.

    You are asking for problems by keeping your levels where they are now. High CH levels can be very problematic for the SWG cell. Further, if something unexpected goes wrong that drives up the PH, or changes the TA significantly in either direction, there can easily be scaling in the pool as well. The PH has a habit of going up to around 8.4 if you don't pay close enough attention, should that happen there will be expensive problems.

    The PH inside the SWG is far higher than it is in the pool, which can lead to CH scaling of the SWG at high CH levels. PH fluctuations are common, expecially at low TA levels, and can easily drive you into scaling conditions pool wide before you notice. You can also run into problems when keeping the TA very low and not using borates. When the TA goes too low, and without borates, the PH tends to fluctuate much more than it will at slightly higher TA levels. With TA around 50 you are probably alright, but it doesn't need to go down very much before there will be problems.

    CYA at 30 is just fine with a large SWG, aside from the fact that you burn through the cell lifetime at more than double the rate you would at a higher CYA level. Given the price of AutoPilot replacement cells, most people don't want to do that.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Is there anthing wrong with high levels of calcium.

    JasonLion.

    Thank you for the quick reply.

    I forgot to mention I do have an acid feeder so that should help, although I have not yet replaced the currently broken one with the replacement I have.

    I do check the SWG cell once a month, but I will check it weekly to see if there are any issues of calcium build up and will advise if there is an issue or not.

    Currently there seems to be very little swing in the pH. The water in our particular area of Hawaii is very, very, soft. It has always been the case that when the alkalinity is say 70 ppm that I am fighting an acid war with the pool no matter what the calcium level was if 600 or lower, if the alkalinity settled at 60 ppm as was the case until recently there was less of a an acid war, but now that it settles at 50 ppm just raising it by 10 ppm starts the acid war over again, why I have no idea. Since raising it to 900 ppm of calcium this has slowed down considerably and leaving the alkalinity at 50 ppm.

    The salt cell runs at a 36% setting, at Power Level 2, for 5 hours at 78 F. The PoolPilot techs thought that a low setting for a chlorine level of 5 ppm for a relatively short 5 hour run, and stated that it should last a long time, were they incorrect in their assumption? I am not an electrical engineer so I really would not know the answer. The cell is about 3 years old, maybe a little older.

    I see the valid points you are making and the necessity of me being more vigilant, although I am fairly vigilant as to upkeep. I agree that this is certainly would not be a good way to go if one only checks the pool once a week. And thank you pointing out this could be an expensive problem, if things do not work out, and I will report it, I will go back to using lots of good old "Arm and Hammer" and lots of muriatic to control my bouncy situation of the past. But to do that I must get my acid feeder replaced first as I do not have the time constantly replace acid, this is why I changed to 900 ppm but as you point out I maybe just be opening the pool to other issues.

    Thank you for your detailed answers, your points are well taken.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  4. #4
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    Re: Is there anthing wrong with high levels of calcium.

    Add 50 ppm borates and the pH will settle in at about 7.7 to 7.8 and stay there. Get the calcium down to 250. As Jason said, you're asking for a scale formation problem. You may not even see it happening. It sort of like watching the kids grow, they hit a threshold and you say to yourself, "How did they get so big?" except now you're going to say,"How did it get like this?"

    Scott
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    Re: Is there anthing wrong with high levels of calcium.

    With an SWG system, you generally want the CSI to be slightly negative. So while it is correct to increase CH when you have such a low TA, you went too far. Your "acid war" subsided because your TA went down to 50 ppm, not because your CH was higher. It is TA that results in carbon dioxide outgassing that causes the pH to rise faster. The CH doesn't affect that as far as we know.
    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
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  6. #6
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    Re: Is there anthing wrong with high levels of calcium.

    Quote Originally Posted by smallpooldad
    The salt cell runs at a 36% setting, at Power Level 2, for 5 hours at 78 F. The PoolPilot techs thought that a low setting for a chlorine level of 5 ppm for a relatively short 5 hour run, and stated that it should last a long time, were they incorrect in their assumption? I am not an electrical engineer so I really would not know the answer. The cell is about 3 years old, maybe a little older.
    With CYA at 30 and a large SWG (which you have) everything will work just fine, and the cell will last a good long time. However, the cell will last more than twice as long if you raise the CYA level up to the 70 to 80 range. Higher CYA levels mean less total chlorine lost to sunlight, which means an even lower percentage and or power level for the SWG, which means a longer cell life. So what they told you is essentially true, but it misses an opportunity to have everything work just a little better and last quite a bit longer than the way you have it now.

    By the by, using The Purple Stuff helps reduce the chances of calcium scaling and metal stains. However, at higher CH levels you will need to use more of The Purple Stuff than you were using before to have the same level of protection from calcium scaling and from metal stains than you would need to use at lower CH levels.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  7. #7
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    Re: Is there anthing wrong with high levels of calcium.

    What is the interior surface of your pool? Plasterers want the calcium to be between 200-400 ppm.

    Like the others have said, you are asking for scaling issues at that high of a level.

  8. #8
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    Re: Is there anthing wrong with high levels of calcium.

    Bruce, it's CSI that determines the protection of plaster. The 200-400 is just a guideline, but if the pH or TA are low, the CH needs to be higher to keep the water saturated with calcium carbonate which is what prevents that compound from being dissolved from plaster.
    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
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    Re: Is there anthing wrong with high levels of calcium.

    Not sure why smallpooldad is getting all this grief. He stated that he is vigilant and that his CSI is negative. This may not be the best setup for pool owners that do not pay attention to their pool. But since this gentleman is being careful and seems to understand his situation he should be fine. Heck, he is saving money by not dumping acid in his pool all the time. Yea if something changes he could be in a scaling situation but since he is careful I say "Good for you".
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
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  10. #10
    Administrator JasonLion's Avatar
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    Re: Is there anthing wrong with high levels of calcium.

    Quote Originally Posted by benavidescj
    Not sure why smallpooldad is getting all this grief. He stated that he is vigilant and that his CSI is negative. This may not be the best setup for pool owners that do not pay attention to their pool. But since this gentleman is being careful and seems to understand his situation he should be fine. Heck, he is saving money by not dumping acid in his pool all the time. Yea if something changes he could be in a scaling situation but since he is careful I say "Good for you".
    smallpooldad started off by asking what was wrong with high calcium levels. We are simply answering that question. It happens that the answer includes significant risk of causing a multi-thousand dollar problem - pool wide calcium scaling - if there were even a minor lapse in vigilance. The risk to the SWG cell is also significant, even with perfect vigilance.

    Also, as smallpooldad stated in his first post, his CSI is positive.

    Our mission here at Trouble Free Pool is to teach a system of pool care that is simple, inexpensive, and trouble free. CH levels lower than the ones smallpooldad is currently using are simpler, less expensive and significantly more trouble free.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  11. #11
    Senior Member benavidescj's Avatar
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    Re: Is there anthing wrong with high levels of calcium.

    Quote Originally Posted by JasonLion
    smallpooldad started off by asking what was wrong with high calcium levels. We are simply answering that question. It happens that the answer includes significant risk of causing a multi-thousand dollar problem - pool wide calcium scaling - if there were even a minor lapse in vigilance. The risk to the SWG cell is also significant, even with perfect vigilance.

    Also, as smallpooldad stated in his first post, his CSI is positive.

    Our mission here at Trouble Free Pool is to teach a system of pool care that is simple, inexpensive, and trouble free. CH levels lower than the ones smallpooldad is currently using are simpler, less expensive and significantly more trouble free.
    Jason, your points are well taken. However, I ran his numbers in pool calculator, and unless I made a mistake, his CSI is actually negative 0.17 not positive 0.17. This means he is not currently at risk of scaling. I was just saying smallpooldad seems to be knowledgeable about his situation and in his situation he is ok. We should be able to give advice to everyone including smallpooldad who wants to work at the edge of "Good". What I have a problem with is us telling him he HAS to do something instead of just advising him of the risks without dictating what he needs to do.
    In the end, the CH guidelines are that, a guideline. For new pool owners you should stick to the guidelines so you don't get into trouble. But once you understand the risks you should be able to work outside the guidelines without doing damage and actually be operating in a better situation for you.
    I personally like working closer to 0 on the CSI but obviouly on the negative side. I too am vigilant, if not anal, with my chemistry. I like it when others operate like I do because it shows they care about their pool.
    Yea, this is not for everyone and should be pointed out. But for those who wish to do it, know the risks and be warned. You take your eye of it and you will be in a world of hurt.
    Carlos
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
    How to shock your pool

  12. #12
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    Re: Is there anthing wrong with high levels of calcium.

    Quote Originally Posted by chem geek
    Bruce, it's CSI that determines the protection of plaster. The 200-400 is just a guideline, but if the pH or TA are low, the CH needs to be higher to keep the water saturated with calcium carbonate which is what prevents that compound from being dissolved from plaster.
    Agreed, and understood 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.

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    Re: Is there anthing wrong with high levels of calcium.

    Quote Originally Posted by benavidescj
    I ran his numbers in pool calculator, and unless I made a mistake, his CSI is actually negative 0.17 not positive 0.17.
    You are right. I assumed he was reporting the number correctly, but it's actually negative as you describe. So he's actually OK and can certainly monitor the salt cell to see if scaling occurs and clean as needed. Sorry, smallpooldad. I assumed the 0.17 was +0.17, but it's not.
    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
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    Re: Is there anthing wrong with high levels of calcium.

    Thank you to one and all for your comments.

    My apologies for not indicating the CSI were negative, this would confuse me as well.

    I have decided that I will continue with my present course of action and report back as concerns scaling issues be they there or not.

    I do wish that when people are helped on this site that they would report back as to which suggestion helped the most, sadly a percentage do not, so obviously this is unhelpful to others with similar issues.

    I cannot use borates as my grand children have a dog. Although I did use them before with salt but it seemed to me I was having a hard time controlling the pH with the acid feeder. I am not sure why. Someone did explain why in a post to another person if I remember correctly but I cannot find that post.

    As to higher CyA I prefer to keep it in the 30 -35 range as I have not seen enough evidence from long term trials regarding its side effects on health. I do realize and agree that this might shorten the life of the SWG cell, by how much only time will tell. So I am not disagreeing but just being cautious, maybe someday I will be convinced enough to go to 70 -80 ppm. I realize the health concern sort of contadicts the fact of my using "The Purple Stuff" without long term testing but the stain issues where driving me insane. They are now gone for the most part and I am very happy with the look of the pool surface and no longer have to treat it with the Ascorbic Acid treatment every so often.

    Jack's Magic "The Purple Stuff" has been nothing short of miraculous in controlling both the removal of old scale and the stopping of iron stains being deposited on the pool, I use to use "The Magenta Stuff" but that kept upping the phosphate level to quickly until within a number of months it reached 4500 ppm, so I drained. "The Purple Stuff" adds very little phosphate, as I have upped the calcium ppms I will call them to see if I need more and will report back, although the pH at 7.4 is where they suggested I keep it (7.2 - 7.4).

    An interesting point, I believe, about having the very, very soft water we have is that it has it's pluses and minuses. According to some studies the island of Oahu where Honolulu is situated has some of the finest drinking water in the nation, although due to volcanic filtration it does contain some Chromium 4 (I am not sure of the number) but fortunately in relatively low amounts. Our own Water Board report, for our area of Honolulu using 3 wells, notes only minute amounts of contaminate from two chemical sources and they are far below the allowed amount. On the minus side when I used borates I only need approximately half the amount to raise the pH by what was suggested in the "Pool Calculator" so it seems our water is more sensitive to small amounts of chemical. Why this would be so I have no idea. It could be that having slightly harder water may be more optimal for pools in general.

    Once again thank you for all of your points they were very interesting and the discussion, feedback and answers certainly clarified a somewhat cloudy subject, please excuse the pun.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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    Re: Is there anthing wrong with high levels of calcium.

    Quote Originally Posted by smallpooldad
    As to higher CyA I prefer to keep it in the 30 -35 range as I have not seen enough evidence from long term trials regarding its side effects on health.
    This file gives detailed info on the health effects of Cyanuric Acid if it were to be accidentally ingested. The No Observed Adverse Effect Limit (NOEL) is 150 mg/kg/day. Even for a 20 kg (44 pound) child, they would have to drink over 37 liters (nearly 10 gallons) of water per day to reach this limit. Also, as noted in this same file, "continuous-dose automated in vitro dermal absorption studies conducted with isocyanuric acid demonstrated minimal absorption through rat, hairless guinea pig, human, and Test Skin (Moody: 1993)". The daily intake through skin for a 60 kg person is 5 µg/kg/day so negligible compared to the NOEL level. The paper on skin absorption is here.

    So your concern about CYA toxicity is way, way off base. There are many other chemicals that you might be concerned with such as long-term effects of chlorinated disinfection by-products (probably in the risk range of less than 1 in 1 million), but CYA would not be near the top of anyone's concern list.

    Quote Originally Posted by smallpooldad
    On the minus side when I used borates I only need approximately half the amount to raise the pH by what was suggested in the "Pool Calculator" so it seems our water is more sensitive to small amounts of chemical. Why this would be so I have no idea. It could be that having slightly harder water may be more optimal for pools in general.
    The Pool Calculator does not do exact pH calculations and in particular such calculations are for a TA level closer to 80 ppm so at your lower TA level it would take less acid to move the pH, with or without the borates though the borates should require more acid for the same pH move. Again, it's The Pool Calculator that was off -- I doubt that the borates had the effect you describe in absolute terms.
    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
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  16. #16
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    Re: Is there anthing wrong with high levels of calcium.

    Chem Geek,

    Thank you for your reply.

    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. 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.

    I would prefer that the CyA be safe and useful at 70 -80 ppm as this would indeed lengthen the life of my cell, but I prefer to be more conservative in my approach especially as the world we live in is so litigious. I am professionally involved with attorneys and know how very difficult it can be for defendants even when they are entirely guiltless to prove their innocence. After having read many of your comments I personally believe in what you write but I would still move to side of being more conservative until these issues are fully resolved on an industry wide basis. My family and I am not the only ones who swim in our pool., if we were I might indeed try 70 ppm.

    Regarding borates, thank you for the answer that explains why I had such an odd reaction. Unfortunately because of the dog I am unable to use them.

    I did note that if I raised the CyA to 70 the HOCL on your "PoolEquations" spreadsheet the HOCL as ppm of CL would be 0.80 (too high I know) and then fall to 0.30 (too low? or compensated for by other factors) and the CSI would go from -0.17 to -0.33 so I would need to add more calcium. If I added 50 ppm borates this would further increase the negativity of the CSI by -0.07, but this is not an issue for me as I cannot add borates. 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.

    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.

    But:

    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.

    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).

    Thank you.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  17. #17
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    Re: Is there anthing wrong with high levels of calcium.

    Quote Originally Posted by smallpooldad
    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.

    Quote Originally Posted by smallpooldad
    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.

    Quote Originally Posted by smallpooldad
    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).

    Quote Originally Posted by smallpooldad
    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.

    Quote Originally Posted by smallpooldad
    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.

    Quote Originally Posted by smallpooldad
    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
    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"

  18. #18
    Senior Member Ohm_Boy's Avatar
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    Re: Is there anthing wrong with high levels of calcium.

    If you are really worried about getting sued by someone who swims in your pool, you can always defer to your local pool store experts and use trichlor pucks and dichlor powder, and summarily bring your CYA up far beyond 100 and have virtually no sanitization at all. Of course, the pool would be far less safe, but you'd have a paper trail, so you'd be covered.
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

  19. #19
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    Re: Is there anthing wrong with high levels of calcium.

    Chem Geek,

    Thank you for a really superb reply and all the work you put into it, I feel that this is one of the shortest , most concise, and best explanations of the interrelationships of the various component chemicals that make up pool water I personally have ever read, especially as it relates to my case of higher calcium and yellow mustard algae.

    I will go with your recommendations. In the Summer the pool might go to 80 F or 82 F, as 16 - 24 mph trade winds blow over it about 90+% of time, on very rare days with no wind it might go to 86F for a few days. And yes mustard algae is what occurs if the chlorine gets too low, sadly it is nearly endemic in this area of Oahu at least according to the pool store owners, my personal experience, and those of our friends with pools, I cannot speak for other areas of Hawaii.

    In Hawaii, and other parts of the world, there is a type of algae that will live in both fresh and saltwater up to 79 F, although that could change, that is why I never let anyone swim in the same outfit if they just came back from the beach. I also make them shower, not sure if this really helps. I have always done this for 16 years or so, long before they discovered this type of algae. See here:

    http://www.sciencedaily.com/releases...0120151633.htm

    Early this morning I checked the SWG cell and there was no calcium build up on the cell, I think this is week 3 (have to check my records when I get home) of the higher 900 ppm, so it seems no issue there. I will continue to check weekly.

    Thank you for your help it is much appreciated and yes as I have a very high trust factor for your research and opinions I am convinced.
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

  20. #20
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    Re: Is there anthing wrong with high levels of calcium.

    Chem Geek

    Update:

    My PoolPilot SWG controller 75003 went out (see other post in SWG section), just around the time I wrote the last post. I ordered a new one which came in yesterday and will have it, and a new acid pump which failed earler, hopefully installed by a licensed electrician on Saturday.

    However I did up the the CyA to 50 from 30, and yes the the TA is now holding at 60, at a temperature of 78F. Acid consumption is still very low despite raising the chlorine to 10, the reason I raised it to 10 is only temporary as I have been busy lately and worry that I may get stuck on an outer island for 2 days or more and this gives me some latitude, as my wife is loath to mess with any kind of chemicals, except those one puts on one's skin. The chlorine has fallen as low as 6 without any issues regarding yellow/mustard algae. I think I will keep it in the 6 region once the the units are installed, so long as there are no issues with yellow/mustard algae, if there are I will report back. Anyhow I still have some old faint tannin stains on the wall that only I think I notice so it will not hurt. My next door neighbour thinks I will have "Died of Perfectionism" wriiten on my death certificate.

    Raising the calcium to 900 certainly seems to help lower the usage of acid when the pH is maintained at 7.4.

    So you of course were dead right and I was too cautious and wrong, on the CyA.

    Thank you for all the help it is greatly appreciated
    10,000 gal plaster pool,3/4 hp WhisperFlo pump, Sta-Rite Great White GW9500 pool cleaner, Hayward 300 lb Sand Filter
    Use Magenta Stuff for Iron and Silica control.
    Balance: pH 7.7 Cl 7 -8 Alk 70-80 CH 325 CyA 30 in winter - 50 in summer NaCl 1010 TDS 1200

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