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Thread: Can I use Calcium Hypochlorate to super chlorinate my pool?

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    Can I use Calcium Hypochlorate to super chlorinate my pool?

    As the subject says, can I use calcium hypochlorate to super chlorinate my pool? I am using an SWG and I just drained half the pool and filled with pond water and I need to clear it up. I have the cal hypo from Leslies (called power powder) that I got before the SWG, figure I might as well use it if it won't cause problems.
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    duraleigh's Avatar
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    You can certainly use it. Keep in mind that it is usually about 33% (or thereabouts) calcium which will add to the CH in your pool.

    One time or even occassional usage seldom has any affect. Prolonged usage of Cal Hypo (and the subsequent large increase in CH) is not a good thing.

    One interesting side-effect I noticed while using it in my pool....massive doses of it (straight into the skimmer) left calcium deposits on my pump strainer basket lid....clouding it over. A little muriatic cleared the lid right up but it taught me to apply it in a more restrained manner.
    Dave S.
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    well I'm draining and refilling now, would like to use the rest of the cal hypo, but it clouded the water over this past time and it wouldn't clear up, dumped in acid, let the filter run, and no improvements.
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    If it clouded up and stayed clouded up, then the CH or TA levels were probably high to start with. Next time, I would test those levels (and pH) before using Cal-Hypo for shocking. With circulation to thoroughly mix it plus acid addition to lower the pH (and possibly the TA if aeration is also done), then it will clear up, but it takes days. It does sound to me like the pond water might have been high in CH or TA for whatever reason.

    The other possibility is that after addition of the pond water, the chlorine got used up (oxidizing organics; fighting algae) and an algae bloom was starting since that looks cloudy before it gets to full green. This seems less likely given the super chlorination with Cal-Hypo, but it is possible depending on how much there was for chlorine to kill or oxidize in the pond water.

    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"

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    Well I have refilled the pool again, did another 50% drain and refill as my stabilizer was too high. I finally have it down to around 100 or so. God knows where it was when it started as this is the second 50% drain. I just checked my levels and i'm at 7.2 PH 120 TA 10PPM or more free chlorine, test stick only goes up to 10PPM. stabilizer at 100.

    So I'm thinking that if I'm still off the charts on FC after adding all this additional new water from the pond that has no chlorine or anything, I tested that water before, then I maybe way way way overdid it with the cal hypo a few days ago.
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    If the CYA was through the roof, then even with a relatively high FC you may not have had enough to combat an alage bloom. If your CYA is now 100 ppm and that's after a 50% dilution, then it could have originally been over 200 ppm CYA. Even 20 ppm FC with 200 ppm CYA will not kill algae faster than it grows when it's in a "bloom". You'd need at least 40 ppm FC with 200 ppm CYA to kill the algae slowly or 80 ppm FC to kill it more quickly but that's pretty impractical. The only solution with very high CYA is a partial drain/refill to dilute it (or a near complete drain/refill when it's extremely high).

    The test stick you are using may not be measuring just Free Chlorine, but could instead be measuring Total Chlorine. It is much better to get a Taylor K-2006 test kit or the TF100 test kit from tftestkits.com.

    The CYA most likely came from your previous use of Trichlor pucks/tabs and/or Dichlor powder which is in products like Leslie's Chlor-Brite.

    Anyway, your drain/refill regimen is the right thing to do and you should continue it until your CYA gets to a manageable level closer to 50 ppm. That way, the chlorine you use to shock the pool will be able to kill any algae. You can then use unstabilized chlorine products, such as unscented bleach or chlorinating liquid (or Cal-Hypo, though that raises Calcium Hardness) to keep the CYA from climbing.

    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
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    down to more like 100 on the CYA now. I have a SWG so I'm assuming my FC should be around 4.5PPM. It is still sitting at 10PPM in the pool now so my main thing is waiting for the water to clear I believe.
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    With the SWG, a CYA level o 60-80 ppm should be OK. The superchlorination in the SWG cell helps, but yes you will still need a higher FC level until the algae is killed off. If you keep at least 20 ppm FC, then you should stay ahead of the algae, but more would go faster (normal shock level is 40% of the CYA level, but that's pretty high at 100 ppm CYA). With a FAS-DPD chlorine test kit, you could test accurately up to 50 ppm FC. It's hard to test with an OTO or DPD chlorine test.
    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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    well the water is still cloudy. I drained about 50% again and used no cal hypo. stabilizer is at 100 now, FC was at 10ppm, down to 3ppm now. Water is a nice shade of blue. PH is at 7.8. TA around 120. Everything is good. I just can't get the water clear.
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    Cloudiness is either 1) poor filtration or 2) developing algae bloom or 3) over-saturation with calcium carbonate. So try taking a bucket of pool water and add some bleach to it (be generous and add several ounces per gallon). If the cloudiness dissipates or falls to the bottom after about 30 minutes, then the cloudiness is from algae and you need to keep the chlorine level higher in your pool (at least 20 ppm if not higher) for a longer period of time. When chlorine levels drop in a pool, in particular overnight, then the chlorine is getting consumed most likely fighting algae. See if you can measure the chlorine level after the sun goes down and then again early the next morning and let us know how much it drops (and what it started at).

    If the bucket test doesn't have the water clear up, then take a fresh bucket of pool water and add some acid to the bucket to lower the pH. If the cloudiness goes away, then the problem is an over-saturation of calcium carbonate. I don't see where you ever measured your Calcium Hardness (CH) level -- perhaps it is very high, but it would have to be really high, like 1000 ppm or more, with your other numbers to show cloudiness. Lowering the pH some will help, but lowering the CH would be needed as well through dilution with lower CH water (you can test the CH of your fill water as well).

    If the above two bucket tests don't clear the cloudiness, then check your filter to see if it is clean and be sure you are filtering frequently enough -- at least one turnover per day, possibly more. If you have an above-ground pool without a floor drain, then if the cloudiness seems to be more near the bottom of the pool then the circulation is poor and you can use a flocculant to clear things up faster -- OMNI Liquid Floc Plus.

    The one other possibility is, gulp, high phosphates. I say "gulp" because we haven't sorted out what really goes on with them -- we know that up to around 3000 ppm or so that they are no problem, but some people swear that at high levels that chlorine gets rapidly consumed and that the pool gets a strange persistent cloudiness, so getting the phosphate level tested is something else to try. If it's high, then there are expensive phosphate removers that can be used.

    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"

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    I have been adding acid, and the FC only came down yesterday because I couldn't run the SWG at all. I will clean the filter and let it keep filtering.

    The pool was filled from pond water, I can't see it being extremly high in CH and I haven't added any Calcium since the 50-60% drain/refill.
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    well I had my water tested at Leslies today. CH was 260. PH they claim was 8, but I think probably a little lower because chlorine levels are high as I dumped in 4 gallons of bleach. CYA was 60. TA I believe 120 and yet the pool water won't clear. Its a nice shade of aqua blue, but I can't see the bottom.
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    JasonLion's Avatar
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    The PH might be lower, because of the high chlorine level, or it might be higher, because some PH tests will read around 8.0 even when the actual level is much higher.

    Assuming Leslie's test results are right, your calcium saturation would be between 0.4 and 0.5. That is high enough to cause calcium clouding in some situations (particularly when adding cal-hypo) and more than high enough to continue existing calcium clouding. You need to bring the PH down to 7.4 or below to start clearing any calcium clouding (again assuming their numbers are right).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    I added more acid and it does look like it is clearing a bit, I may go add a bit more and see if I can get it fully cleared.

    Why do they sell stuff like cal hypo if it just keeps adding a substance that can't be removed?
    8000 gal diamond brite pool with 650 gal spillover spa, Pentair 3hp VS pump. Jandy Cartridge filter and Jandy Heat Pump. Jandy PDA automation system with 2 Pentair Laminars. SmartPool NC74S Robotic Pool Cleaner.

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    You could say the same thing about stabilized chlorine since Trichlor and Dichlor add to Cyanuric Acid (CYA) that cannot be removed. Cal-Hypo adds to Calcium Hardness (CH) that cannot be removed. These can be reduced through dilution, but CYA and CH won't generally go away by themselves (CYA can sometimes get reduced over the winter or possibly slowly over time, but generally it sticks around).

    This is why we recommend using bleach or chlorinating liquid after one gets to the water chemistry levels that they want since these do not add to CH or CYA. You could use Cal-Hypo (or to a lesser extent, Trichlor) in a smaller volume pool with an opaque to UV pool cover to reduce chlorine breakdown from the sun and that had frequent dilution, say from weekly backwashing. In such an environment, some pool users can find they keep their CH or CYA levels relatively constant by adding chlorine at a rate roughly equal to the rate of dilution.

    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"

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    Quote Originally Posted by robl45
    Why do they sell stuff like cal hypo if it just keeps adding a substance that can't be removed?
    Because chlorine is unstable and in some forms poisonous, so you have to add something to it that will stabilize it for transport. There aren't a lot of suitable choices, basically water, calcium, CYA, and lithium. Of these, using water gives you bleach, which isn't as stable as the others and adds lots of mass and volume. Lithium is almost ideal for swimming pools, as it doesn't tend to cause any chemistry problems, but it is dramatically more expensive than the others. That leaves you with calcium and CYA, both of which have problems down the road, but which make for compact and affordable chlorine products.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Jason is of course completely correct. The chemistry of chlorine doesn't allow for a perfect chlorine source -- something very concentrated without extra stuff that is reasonable in cost. This link gives a cost comparison of chlorine sources, but also shows the weight density of chlorine sources where you can see that other than chlorine gas, which is very toxic and must come in pressurized containers that are heavy, Trichlor is the most concentrated form of chlorine so is the least amount of chlorine, by weight, one would need to carry around. Unfortunately, Trichlor adds to Cyanuric Acid (CYA) and it's also highly acidic which means that you have to add pH Up periodically to compensate. When accounting for this, it no longer is the least expensive chlorine source.

    Bleach and chlorinating liquid (i.e. Sodium Hypochlorite) are generally the least expensive chlorine products after accounting for the fact that they are really pH neutral (when chlorine usage is accounted for) and do not have significant "extras" except for water and salt (Sodium Chloride). However, they are the least concentrated forms of chlorine so are much more weight to carry.

    As Jason pointed out, Lithium Hypochlorite is nearly 5 times more concentrated in chlorine by weight than chlorinating liquid and over 9 times more concentrated than bleach. It's only about half as concentrated as Trichlor. If it weren't so darn expensive, we'd all be using it. It costs (for equivalent amount of chlorine) 4-5 times as much as bleach and chlorinating liquid and over 3 times as much as Trichlor accounting for pH adjustment.

    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"

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