What Kind Of Shock Do You Think Is Better?

[maddie0929]

ok my husband and I have a debate.. he says the powder shock is better.. I say the liquid. We usually use the liquid kind but today I tried the powder kind.. just to see.... we have used the powder kind before but I can't remember if it did as well as liquid.

Also, I have seen Arm and Hammer shock (plus something else??) at Wal Mart.. has anyone used it? Just wondering before I spent $$$ on it.... looks pretty good....

Thanks!!

[PaulR]

Liquid chlorine, which is basically just double-strength household bleach, is what I use. Every kind of powder adds something to the pool besides chlorine, either calcium or stabilizer, and too much of either is NOT a good thing. Liquid adds nothing else (except a tiny bit of salt... big whoop).

--paulr

[chem geek]

One exception to the powder comment is lithium hypochlorite which like chlorinating liquid or bleach does not increase Cyanuric Acid (CYA) nor Calcium Hardness (CH). It is, however, about 5 times as expensive (or more).

[spookyproud]

Take it from someone who has been struggling with pool problems since we got ours late summer last year. We were only offered the powder shock--which runs about $5.00 per bag. I have had a terrible algae problem that I couldnt seem to get rid of---with their powder shocks and algaecides.

We finally went to a new pool place who offered liquid last week. Our pool has never been cleaner OR easier to care for. The only drawback that I notice is that we cannot swim for 24 hours. I cannot believe the cost of it either!! So much less than the powder. If it means stabilizing my pool quicker and not a lot of other problems added--I will be using the liquid form from now on.

It does not mean to say that if we are going to use the pool and it needs a quick shock---that I would not use the powder but it wont be a weekly thing. I am sticking with the liquid.

[imnay]

Just our opinion from our many years of personal experience.

ALL packaged pool chem products are a huge rip-off. Like 3 pounds of "PH Plus" in a pretty plastic container for like $ 8.00 when you can buy a 50 pound bag of Soda Ash for $19.95 - Alkalinity Increaser - same thing - 8 bucks for a small but very pretty plastic container instead of 50 lb bag of Bicarbonate of Soda for $19.95 (all prices shown are for products that sit side-by-side at our neighborhood hardware store).

Shock - contractor that installed our pool 21 years ago told us the powders were an expensive waste of money and that liquid chlorine by far the easiest and very cost effective to use and we have followed that advice since and it has worked since then.

Never knowing any better all these years we have used a simple 4-way test kit and we learned that if you test often and keep PH and Alkalinity always correct with a good algaecide and great care to keep your stabilizer of choice (chlorine for us) constantly maintained the water stays crystal clear and your need to shock at a minimum.

WOW - sorry, I rattled all that off to say in summary powders in pretty packages in small quantities are a waste of money and for shocking quick and easy nothing (to us) beats keeping a couple of big yellow jugs of liquid chlorine on hand.

Best of Luck

[chem geek]

I'd say the only main exception to the powder/granular chlorine not being a good deal is that Cal-Hypo can often be found at a price rivaling chlorinating liquid or bleach on a "per FC" basis. Of course, Cal-Hypo will increase Calcium Hardness (CH), but if one already has a low CH, say in a vinyl pool, then Cal-Hypo is another alternative. The only main advantage is that it is less weight to carry as it is more concentrated.

I did a cost comparison of chlorine source in this post including the "hidden" cost of pH adjustment needed for Trichlor and Dichlor. Prices have risen since then, but in some parts of the country the Cal-Hypo is less expensive. It shouldn't be used as a regular source of chlorine due to the CH buildup (unless one has a lot of dilution with low CH water), but for shocking it's an alternative in low-CH pools.

[quantumchromodynamics]

Calcium Hypochlorite is a bad choice. It never fully dissolves; and some of the powder falls to the floor. The powder that falls to the floor can cause stains or bleaching. Calcium hypochlorite takes too long to dissolve; and it clouds the water. The residue that ends up on the floor will re-cloud your water when you vacuum or brush.

Sodium hypochlorite (Liquid chlorine or bleach) goes in clean with no residue and very little waiting if you don't over chlorinate. Even for pools that need calcium, it is far better to use the liquid chlorine and add the calcium separately.

[chem geek]

Thanks for reminding me to say that you need to pre-dissolve Cal-Hypo in a bucket of water prior to adding it to the pool. If you do that, then you should have far less residue settling in the pool. As for clouding the water, it's not much different than adding pH Up in that regard. If the water is near being saturated with calcium carbonate, then adding either calcium or carbonate will temporarily cloud the water, but this goes away as it dissipates (unless you over-saturate the water). That's why I said it should be used only when the CH level is low so the water isn't near saturation with calcium carbonate.

I've added Dichlor before (when I wanted to raise the CYA level) and even it wouldn't fully dissolve and some settled to the bottom, but Cal-Hypo can be even slower to dissolve. Cyanuric Acid (CYA) is the slowest to dissolve (other than Trichlor pucks/tabs) and can be added in a sock or panty hose hanging over a return (or in the skimmer if there are other ways for the water to flow to the pump).

One should also be careful when adding chlorinating liquid or bleach, especially in a vinyl pool. Until mixed, this liquid form of chlorine is denser than water so can settle to the bottom of the pool and cause some of the same problems you describe with Cal-Hypo. To avoid this, simply pour slowly over a return flow and for extra safety, lightly brush the side and bottom of the pool where the chemical was added.

[quantumchromodynamics]

Even with pre-dissolving the cal-hypo in a bucket and an unsaturated condition, there is still residue and clouding. The undissolved portion can bleach liners or dark plaster. If the undissolved cal-hypo hits white plaster when the ph and/or the alkalinity are too low, it can cause a black or gray stain.

It is unsafe to swim in the pool until all of the cloudiness is gone. The cloudiness can act as a precipitating agent for calcium carbonate scale to form in heaters where elevated temperatures alter the SI or salt cells where the high pH caused by the hydrogen being removed and the carbon dioxide being agitated out of solution also increases the local S.I.

Dissolving cal-hypo in a bucket is messy, dangerous and tedious.

Plaster pools should always be kept near saturation to protect the plaster. Any negativity in the SI always damages the plaster; and plaster is far more difficult to redo than most people realize.

I cannot think of one single advantage that cal-hypo has over liquid. Even if there is a slight price advantage, it doesn't overcome the serious problems of using cal-hypo. As far as weight, bleach is so available it offsets any density advantage.

Calcium chloride should be added separately if needed.

In addition, if the cal-hypo is 73%, then there are still 27% of mystery garbage chemicals being added to the water.

[quantumchromodynamics]

Furthermore, if you do vacuum residue/undissolved cal-hypo, there will be a large spike in the concentration of calcium and chlorine inside the filtration system, which is not good for your system.

[chem geek]

Thanks for the info. We've seen quite a few users add it pre-dissolved in a bucket and didn't report problems of residue when poured slowly (i.e. if there was residue undissolved in the bucket, they would leave it, but there usually wasn't much or any) and when added to unsaturated pools didn't report any persistent cloudiness, but I'll be on the lookout for the issues you describe. We don't generally recommend Cal-Hypo and usually recommend chlorinating liquid or bleach (6%), but for those who already had Cal-Hypo or had low CH and wanted to raise it along with chlorine (usually for shocking), then we didn't say no to it.

As for what else is in Cal-Hypo, it's not a mystery. Most is sodium chloride salt with some salts of calcium (chloride, hydroxide, carbonate) where this MSDS is typical. The worst are Cal-Hypo tablets since they have very messy binders that don't dissolve and such tablets tend to fall apart too quickly. When I refer to Cal-Hypo, I am usually talking about granular which should not need any binders.

I agree that Cal-Hypo in a plaster pool already saturated with calcium carbonate as the water should be isn't a good idea. I was referring mostly to vinyl pools where the CH may already be low or to fresh fills where the CH in a plaster pool may be low. However, I agree that calcium chloride is a better source of calcium for increasing CH (though even those pellets don't dissolve immediately when added and I've had to brush the bottom to get them to dissolve -- but as you point out, at least they aren't chlorine).

As for your arguments of cloudiness causing precipitation in saturated pools, the same could be said of pH Up products since that is sodium carbonate that both raises pH and TA quite a lot. It definitely has the effect of cloudiness in saturated pools -- I've seen that in my own pool, for example, years ago when I used to use Trichlor tabs. Though now I don't usually ever need to add it (or Borax, as an alternative) because I use only chlorinating liquid, I've never seen a problem with it. It, too, can clump into harder calcium carbonate chunks that then need to dissolve so pre-dissolving could help here as well. Are you sure that with Cal-Hypo than any chunks that are formed aren't calcium carbonate rather than undissolved Cal-Hypo? Are you recommending against using pH Up as well? If you say one should not swim when there is cloudiness, I presume that is so you can see anyone who is drowning and be at the bottom of the pool -- in that case, cloudiness from pH Up would be just as much of a problem.

As for calcium carbonate scale in salt cells, that is of course true in general which is one reason why most cells today switch polarity periodically. One can minimize the problem by having the S.I. slightly negative (not lower than -0.2, usually) and by using 50 ppm Borates in the pool as an additional pH buffer (which has the pH not rise as much at the plate where hydrogen gas is generated and gets higher in pH).

On another topic, we've got this little debate going in this thread on whether it's OK to pour chlorinating liquid or bleach into the skimmer rather than over a return flow in the pool. What are your thoughts on this? Clearly, acid in the skimmer is an absolute no-no since the acidity is so low that dilution simply doesn't help (Muriatic Acid has a pH of -1 so even a 100:1 dilution only gets that to a pH of 1). I've calculated that the active chlorine level isn't horrible (due to the high pH), though is high.

Also, what are your thoughts on adding Cyanuric Acid (CYA) to the skimmer, slowly, to get caught in the filter to dissolve over days (up to a week)? I'd rather see it in a sock or panty hose hanging over a return flow or in a T-shirt, panty-hose or skimmer sock in a skimmer (assuming there is alternate flow since it will block skimmer flow) if one wants to dissolve it quickly. I don't like the idea of it sitting in the filter, but perhaps that depends on filter type since sand and DE are probably OK but I worry about the local acidity in a cartridge filter (since the flow rate is very slow in an oversized filter).

Richard

[quantumchromodynamics]

I try to avoid using pH up. As you noted, using liquid chlorine will usually keep the pH from going too low. If I feel like I need to raise the pH, I will usually use baking soda (sodium bicarbonate) rather than sodium carbonate.

Sodium bicarbonate goes in very cleanly. Yes, I know that it is for raising the alkalinity, but if you add just the right amount, the pH will almost always go exactly where you want it. If I need to avoid raising the alkalinity, then I will use PH up. I find that with limiting the amount of sodium carbonate to a maximum of one pound per five gallons of water and mixing well, the cloudiness can be minimized.

The heater and salt cell should be turned off whenever adding such chemicals, and left off until the cloudiness is fully gone.

Part of my concern is that the high concentrations of calcium could combine with the hydroxides created by the salt cell to form calcium hydroxide and then combining with carbon dioxide to form more calcium carbonate.

I will sometimes dilute liquid chlorine to about 1 to 2% before adding it to a pool. This mitigates the risks by reducing the density and the concentration. Pouring undiluted bleach or liquid chlorine slowly into the flow from a strong return is also good.

I do not generally like adding bleach or liquid chlorine through the skimmer. It is OK if there is no heater or other metal in the filtration system, there is a sand filter and wall returns. The high chlorine will have a detrimental effect on a copper heat exchanger, salt cell plates, brass gate valves, the fabric in a DE or cartridge filter and other such elements. If the pool is plaster with floor returns, the chlorine could cause metals in the water to plate out on the floor around the inlets.

I have never had any problems adding cyanuric acid through the skimmer. How low do you think the pH goes when the cyanuric acid is dissolving?

I can get calcium chloride to fully dissolve to a clear liquid in a bucket before adding by mixing a maximum of two pounds per five gallons of water and by only getting the highest purity. There is never any undissolved solute. I strictly avoid the low quality 77% stuff.

[chem geek]

I have never had any problems adding cyanuric acid through the skimmer. How low do you think the pH goes when the cyanuric acid is dissolving?

Thanks for your detailed response and info. As for CYA, it dissolves slowly, but in an oversized cartridge filter, one could have very low water flow through the CYA and cartridge material and the undissolved CYA is in direct contact with filter material so the pH could get very low locally. I don't know how low -- it's something that can't be accurately calculated in the region of direct contact and very low flow rates -- there is diffusion, but that calculation only works more easily for the water, not the CYA into the fibers of the cartridge material (at least, I don't have any diffusion contstants for that).

1 ounce weight of CYA in 1 gallon of typical pool water results in a pH of 5.2 so that gives a rough order-of-magnitude. It's not anything like Muriatic Acid.

So the CYA concern is just a speculative concern -- nothing concrete.

As for the chlorine levels through the skimmer, if diluted 128:1 as with 1 fluid ounce in 1 gallon, then the pH rises to around 9.2 and the active chlorine (hypochlorous acid) level is around 7.4 ppm, equivalent to around 15 ppm FC with no CYA at a pH of 7.5 so very high, but a brief exposure. Again, not anything nearly as drastic as Muriatic Acid with it's pH of 1 even at 100:1 dilution and similarly relatively brief exposure. The Free Chlorine (FC) is very high at 482 ppm, but most of this chlorine is bound to CYA and for practical purposes not reactive (though it does provide a buffer or reserve of chlorine).

Richard

[chem geek]

quantumchromodynamics,

As I told you, I'd be on the lookout for Cal-Hypo problems and sure enough this post was just made that showed that Cal-Hypo added in a braodcast fashion or via the skimmer both ended up with fading spots on a vinyl liner. Pre-diluting in a bucket and only adding the liquid portion over a return flow is about the only way this could be done with reasonable safety so as you point out it's not a great choice of chlorine for vinyl pools unless you are very careful.

Richard

[quantumchromodynamics]

Even if you're careful, there is almost always some residue that will enter the water. And, what to do about the undissolved sludge that is left in the bottom of the bucket? There is no way to safely dispose of the toxic chlorine sludge. It is my opinion that no one should ever use calcium hypochlorite.

After thinking about your other question, about adding chlorine through the skimmer, more carefully, I am going to recommend that chlorine never be added through the skimmers. There is just too much that can be damaged.

[GRINtync]

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[Trigger]

Hi...

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Thanks

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