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Thread: some chem questions

  1. Back To Top    #1

    Join Date
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    some chem questions

    Hi, have learnt a lot in a few days reading here but have some questions.

    As a new pool owner, I was very uneducated on it water chemistry. Pool was established at the end of our swim season and we are now entering warmer weather again now, over winter I had nil problems, then lifted the cover kids swam for an hour and day or two later I had signs of algae growth. Took a sample of water to my pool shop and followed their recommended procedure to rectify the water chemistry. Having spent quite a few years studding marine life I have a reasonable understanding of sea water chemistry, after purchasing the products recommend for my pool, reading the content I quickly realised there could be cost savings in buying non pool branded chemicals and I was also confused by the recommended schedule in that I was first raising my Alkalinity then Ca then Acid them raising FC and reducing TA.

    Why not raise Alk. & Ca in one step at the same time and in the correct ratio using Calcium Hydroxide solution (Ca(CO)2)? Sure it has to be added slowly to prevent precipitation of calcium carbonate, adding to the skimmer box should help a lot, and I am only assuming CO2 levels in the water would cope. Or better still add some vinegar (Acetic Acid) as a CO2 source, mix a solution prior to adding to the pool, you would have balance of free Calcium ions and free bicarbonate ions in solution that you could dump straight in to the water. And I would suspect nil shift in pH or much less due to not chewing up CO2 from the water column (less Acid required).
    Now for FC, I understand that the shop got me to shock the system with a extremely high level of free Cl, and after reading this forum it may not have been such a bad thing as I first thought due to having some algae starting to be visible. However, since shocking my pool the FC level in off the measurable scale for my testing kits, and my CYA is testing as nil.
    Previously the CYA was tested at 40ppm, I have since added CYA (800mg to 38000L pool) which I feel should have shown an increase of about 20ppm, but still after 48 hours I have of the scale FC and no measurable CYA.
    Question: Could the hi FC level influence CYA test results, using Accucheck strips the only test I have available at the moment for CYA. I am reluctant to dose more CYA till FC is measurable as I would like to aim for CYA of 60ppm.
    I do have a SWG, (Zodiac TRi) and am considering BBB method once I'm more confident with the benefits/hazards of adding Borates.
    I spoke with a supplier of Boric Acid marketed for pool use, after being amazed that 3 pools shops I contacted had no idea that boron were even used for pools, yet one store sold boric acid labelled Optimiser Any way, contacting the supplier I was told 24ppm was the recommended level to use, this is far lower than the 30-50ppm recommended here, what are your thoughts, is 24ppm a bit low, it would feel safer to me, but I would be using it for a reason, no good half doing the job!

    After a couple days reading here I am confident I can get my water chem. sorted once I get more accurate testing kits. Maintaining stable conditions won't be hard, time permitting. When I work I am often away for days at a time, so daily testing will often go un attended. So my aim is to Automate FC and may be pH. Any suggestions on controllers to do this would be great, or any other element worthy to Automation.
    Hopefully with Borates and FC pH automation, testing weekly will be acceptable. I can use less chemicals, less FC and possibly even lower levels of elements.

    Big post for a newbie, if you followed this far I thank you

  2. Back To Top    #2
    Mod Squad Bama Rambler's Avatar
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    Re: some chem questions

    Welcome to TFP.

    It's going to be hard for us to help you without knowing where you're located. Sounds like you're on the right road, knowing that you need a better way of testing.

    The high FC level won't affect the CYA test but your problem is the testing method you're using. Strips are notoriously wrong and especially in the case of CYA.
    Dave J. TFP Moderator
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  3. Back To Top    #3

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    Re: some chem questions

    Quote Originally Posted by Brakel
    ...I was first raising my Alkalinity then Ca then Acid them raising FC and reducing TA.

    Why not raise Alk. & Ca in one step at the same time and in the correct ratio using Calcium Hydroxide solution (Ca(CO)2)? Sure it has to be added slowly to prevent precipitation of calcium carbonate, adding to the skimmer box should help a lot, and I am only assuming CO2 levels in the water would cope. Or better still add some vinegar (Acetic Acid) as a CO2 source, mix a solution prior to adding to the pool, you would have balance of free Calcium ions and free bicarbonate ions in solution that you could dump straight in to the water. And I would suspect nil shift in pH or much less due to not chewing up CO2 from the water column (less Acid required).
    They obviously had you overshooting the TA at first and that was a mistake. As far as adding Calcium Hardness (CH) and Total Alkalinity (TA) at the same time, you can't do that by adding calcium hydroxide which, by the way, is Ca(OH)2 and has no carbonate in it. Calcium hydroxide would raise the CH and the pH. If you wanted to raise the TA, you need bicarbonate, but calcium bicarbonate does not exist (except in solution). You can raise both CH and TA by adding calcium carbonate (which is CaCO3), but this is very slow to dissolve (it's scale and part of plaster) and would substantially raise the pH.

    It is no big deal to increase CH using calcium chloride and TA using sodium bicarbonate. You can get the former in de-icers such as Dowflake and Peladow and Tetra and you can get the latter with Arm & Hammer Baking Soda.

    Quote Originally Posted by Brakel
    Now for FC, I understand that the shop got me to shock the system with a extremely high level of free Cl, and after reading this forum it may not have been such a bad thing as I first thought due to having some algae starting to be visible. However, since shocking my pool the FC level in off the measurable scale for my testing kits, and my CYA is testing as nil.
    Previously the CYA was tested at 40ppm, I have since added CYA (800mg to 38000L pool) which I feel should have shown an increase of about 20ppm, but still after 48 hours I have of the scale FC and no measurable CYA.
    Question: Could the hi FC level influence CYA test results, using Accucheck strips the only test I have available at the moment for CYA. I am reluctant to dose more CYA till FC is measurable as I would like to aim for CYA of 60ppm.
    High FC should not affect a good CYA test, but test strips are notoriously awful for testing CYA. Get yourself a good drop-based test kit. We need to know where you live since not all test kits are available everywhere. If you are in the U.S., then the TF-100 from tftestkits.com or the Taylor K-2006 are your best bets (only the latter is available in Canada). In Europe, you can get the Palintest SP 315C (and the SP 300 FAS-DPD if you can find it). [EDIT] I see you have your location in your post as Australia so see if you can find Taylor kits and if not look for Palintest. [END-EDIT]

    Quote Originally Posted by Brakel
    I do have a SWG, (Zodiac TRi) and am considering BBB method once I'm more confident with the benefits/hazards of adding Borates.
    I spoke with a supplier of Boric Acid marketed for pool use, after being amazed that 3 pools shops I contacted had no idea that boron were even used for pools, yet one store sold boric acid labelled Optimiser :roll: Any way, contacting the supplier I was told 24ppm was the recommended level to use, this is far lower than the 30-50ppm recommended here, what are your thoughts, is 24ppm a bit low, it would feel safer to me, but I would be using it for a reason, no good half doing the job!
    Proteam Supreme is sodium tetraborate pentahydrate which is nearly identical to 20 Mule Team Borax which is sodium tetraborate decahydrate. Proteam Supreme Plus is mostly boric acid. The Supreme dosage chart indicates a "Good" level as 30 ppm and "Best" as 50 ppm. This, along with scientific data found in this link show that algae inhibition requires the somewhat higher levels while pH buffering doesn't require as much. BioGuard's Optimizer Plus is mostly boric acid and has a dosage rate of 1-2 pounds per 1000 gallons of water which would roughly correspond with 20-40 ppm. I'm not sure why your supplier is quoting 24 ppm as a specifically recommended amount.
    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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  4. Back To Top    #4

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    Re: some chem questions

    Thanks for the reply, I have found TFT 100 kits here in Oz and waiting for mine to arrive
    Sorry for the typo, yes Ca(OH)2 is correct, But Ca(OH)2 + 2(CO2) = Ca++ + 2(HCO3-). The only complication is dosing to quick, depleting CO2 causing CaCO3 +H2O, and infact can reduce free Ca and HCO3 ions which is why I sugested using Acetic Acid.
    Ca(OH)2 is dirt cheap and readily available as builders lime or plasters lime.

    Yes it will raise pH, a saturated Ca(OH)2 solution would have a pH of around 13 from memory, the vinager will help reduce pH but for top up use, to maintain 200-250ppm Ca the pH swing will not be huge and easily adjusted if required. The other advantage is you only need to test either Ca or HCO3 as what you change in one the other will always be in a proportional.

    Dissolving CaCO3 would work as well, but its slow to dissolve, you would need to make a reactor to lower pH in the reactor you could use acid or CO2 injection, then from the reactor it would need to be dripped into the skimmer or fast water flow, not as practical.

    Thanks for the heads up on Borate levels. I questions the distributor of BioGuard's Optimizer here in Australia who quoted the 24ppm level to me, this is the reply
    Sorry I mistranscribed my notes, the repeat interval is weekly but as you say this will not make a great deal of difference. A monthly top up of 100 g would probably be a better solution to maintain the levels.

    The label suggests that a check twice a year will enable sufficient control so it is not considered critical to keep levels ay the peak level. A semiannual maintenance would probably entail the addition of half a kilogram of Optimiser.

    An alternate way of topping up the boron levels would be to use PowerChlor as a chlorine boost or Burn Out Extreme as your regular maintenance oxidizer. The former has about 6% and the latter about 9% of sodium tetraborate which will help to make up for dilution and splash out.

    As far as the differences in recommendations between us and the USA, the pool use and maintenance is different. Most pools in Australia are salt pools, using electrolytic chlorinators whereas most US pools are ’fresh’ and use chemical additions to sanitise the water. The increased ionic concentration in Australian water slightly reduces the need for ‘softening’ to give a similar feel.

    If your pool is a salt pool there is a program due for launch next year called Mineral Springs which is an integrated package to maintain soft water with minimum effort. If you are running an Optimiser pool you should be able to adopt the renewal program for Mineral Springs without going through the ‘Convert’ step. If you let your Bioguard Approved Retailer know that you are interested they should be able to keep you informed on the launch date.
    An interesting comment I got from one of the Authorized Resellers when chasing accurate test kits, it would cost you $3000 for accurate test kits and even if we could get them for you, why would we? I said that is a disturbing comment, what do you mean? He continued to state that they offer a free testing service and control the pool water for you, we would loose sales if you could do that, I said, no thanks, I will control my pool and you have just lost any chance of a sale now.
    I am happy to pay a little extra for chemicals, products etc to support local pool shops, they are more than just a chemical supplier, but with attitudes like that I will never support. This is one shop and I'm sure this attitude is among the minority.

  5. Back To Top    #5

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    Re: some chem questions

    Calcium Hydroxide is like Sodium Hydroxide (lye) in that it will raise pH SUBSTANTIALLY. You would have to add a strong concentrated acid like Muriatic Acid (Hydrochloric Acid) to compensate for it. I find it very hard to believe that you can get calcium hydroxide a lot less expensively than you can get calcium chloride.

    You are correct that the hydroxide causes a shift from carbon dioxide to bicarbonate, but this is done at the expense of rising pH and more importantly, it is not permanent if you adjust the pH back down again. TA rises when pH rises and falls when the pH falls, but not by that much and besides, you don't want the pH to rise a lot. The way to increase TA without changing the pH (much) is to add baking soda (sodium bicarbonate). If you added one pound of calcium hydroxide to 10,000 gallons of water, you would increase CH by 16 ppm and the pH would rise from 7.5 to 8.7 (if the TA started at 100) and the TA would rise by 15.7 ppm. So this is completely and entirely impractical, at least by itself. If you also added 40 fluid ounces of Muriatic Acid (31.45% Hydrochloric Acid), then the pH would remain at 7.5, but the TA would not increase and the chloride level would increase by about 19 ppm (measured as ppm sodium chloride). This would be identical to adding calcium chloride directly except for the extra water that is produced from calcium hydroxide with hydrochloric acid.

    Ca(OH)2 + HCl ---> CaCl2 + H2O
    Calcium Hydroxide + Hydrochloric Acid ---> Calcium Chloride + Water

    So you really need to get this idea of using calcium hydroxide out of your head unless it is so much cheaper than calcium chloride that adding it and muriatic acid (added separately to the pool) is actually more economical than adding calcium chloride.

    Vinegar (acetic acid) is not nearly a strong enough (nor concentrated enough) acid to compensate for the calcium hydroxide and it will also be adding organics to the pool. It's just a bad idea.

    As for the differences in the U.S. and Australia, this isn't really true anymore. Most new in-ground pools in the U.S. now have saltwater chlorine generators (SWG). It is true that most above-ground pools do not and many previously installed in-ground pools do not, but the reason for using the borates isn't so much for the soft water feel (since salt will give you that) but rather for its algicidal properties and those are stronger at 50 ppm. It is also a pH buffer and that is helpful for SWG systems since the pH tends to rise in such pools and the pH buffering also helps reduce the scaling in the salt cell.
    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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