Bleach v. Tabs v. Powder

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goodgnus

0
Jun 2, 2008
15
Phoenix AZ
I am trying to determine a single chlorination method that I can use this summer and which one is most cost effective yet also the simplest method.

6% bleach, $1.30 gal (will require weekly bleach runs, suppose I should factor in my time and cost of gasoline to purchase).

73% calcium hypochlorite powder, $135 for 100 lbs.

99% calcium hypochlorite tabs, $96 for 50 lbs.

My plan for the powder was to determine from a 0ppm baseline, how many ppm increase I get from 1lb, the degradation of that level to 0ppm again (in # of days) and then divide 1lb by the # of days and add that much powder to the pool on a daily basis to keep the chlorine level consistent. I plan to check the chlorine level every 3 days thereafter and adjust the daily dosage as necessary. Also easy to shock using this method since it's already in powder form.

I hesitate to use tabs because it seems I can never get the calculation right (# of tabs in floater, floater setting) to keep the chlorine level consistent, either the tabs don't dissolve fast enough (due to cooler water, not large enough floater) or they dissolve to quickly in warm water and I am not checking the floater frequently enough and there is inconsistent chlorination. Also, since I'm a cheap ******* it's more difficult to shock using tabs because I have to put them in a canvas sack and crush them with a hammer to get powder.

From a cost and simplicity perspective it seems the powder is the way to go. Would you agree? Anything I'm forgetting?

Thanks

-Tom
 
Tom,

Welcome to the forum! You've had a couple of other post replies, but I believe this is your first thread.

I can guarantee you that there is no such thing as 99% Calcium Hypochlorite you can buy for your pool. Either that's Trichlor pucks/tabs or a mistake of some sort in labeling. Cal-Hypo is usually sold as 65% or 73% and sometimes as 48% (or numbers close to these).

As for a cost comparison of chlorine sources, you can take a look at this post. Note that the true cost factors in the additional base (pH Up or Borax) that needs to be added to Trichlor (and Dichlor). Your $1.35 per pound for Cal-Hypo is an exceptionally good price and would make that the least expensive source of chlorine.

Cal-Hypo is often a reasonably priced alternative. The only real issue with it is that it will increase our Calcium Hardness (CH) level over time. For every 10 ppm Free Chlorine (FC) added by Cal-Hypo, it will also increase CH by 7 ppm. This rule is independent of the concentration of Cal-Hypo. Since the CH level is usually 200-300 ppm or so, it is possible for this slow rise in CH from Cal-Hypo to be offset more easily by more frequent backwashing or other dilution. It's not as critically serious as a rise in CYA that can lead to an algae bloom. At some point, a high CH, along with other factors, can lead to scaling, but that takes a lot of calcium to get there.

Note that Cal-Hypo is sometimes a little slow to dissolve so some people pre-dilute it in a bucket of pool water to help dissolve it and mix it up and then pour it over a return flow. You want to make sure that chunks don't settle to the bottom of the pool -- especially in a vinyl pool -- and can use a pool brush to help ensure mixing.

Richard
 
Richard,

Thanks for your response. I will have a look at the tabs next time I visit the pool store, I am certain it was 99% but did not look at the chemical makeup. The CH at $1.35 is a special price due to a 20% discount coupon on chemicals right now, the 100# bucket is usually $168.00 which I gather is also a decent price.

My water is about 2 years old and I recently added 5lbs of CYA (to 22k gallon plaster) because the level was close to 0 per the store's water test (I did not add CYA at startup). I do not know what TH currently is, but I have had to deal with elevated levels of TDS before and did a full drain and acid wash about 2 years ago as well as a sand replacement.

I think I will go with the CH as it's the most cost effective / easiest to use and esp given the fact that my CYA levels are ideal at the moment. The only other chemicals I plan on using this summer are a phosphate remover, ph balancers (MA or SA) and a clarifier as necessary. Having had algae problems in the past and doing such drastic things as using severe amounts of algaecide and dumping 25# of CH into the pool at once, I am making it a point to focus on preventative maintenance from now on.

-Tom
 
$135 for 100 lbs is a really good price for cal-hypo.

Your CH level is already 250, that means that you don't want to use cal-hypo all season. I don't know what size your pool is, but assuming a 25,000 gallon pool (fairly large), 100 lbs of cal-hypo would add another 240 ppm of calcium. That would put you at 490, which is too high.
 
Tom,

I concur with what Jason and duraleigh are saying. It all depends on the size of your pool and rate of dilution. A smaller pool that has a sand filter getting backwashed weekly could keep the CH lower assuming that the fill water was low in CH. Also, a vinyl pool with an initial low CH is also another possible candidate for Cal-Hypo, at least for a while. However, in a hot sunny environment, evaporation will have the fill water CH simply add to your existing CH so it can get too high if you also use Cal-Hypo. If you use a pool cover, then that can significantly cut down evaporation.

If you were to use Cal-Hypo and you didn't have enough dilution (say, from backwashing), then you'd have to periodically do a partial drain/refill to lower the CH. If the fill water is high in CH, then with evaporation you might have to do a partial drain/refill anyway even if you didn't use Cal-Hypo. So that would need to be factored in to your cost/benefit analysis. With chlorinating liquid or unscented bleach, you don't have these problems as no extra CYA nor CH gets added.

Richard
 
Thanks guys.

While I do like the BBB concept very much and would like to strictly use bleach, obtaining and storing bleach to use as my primary chlorination method is a bit of a task. I have my water tested twice a month and I will keep an eye on the CH levels and do some mitigation as they rise.

The evaporation rate is high here in the summer, but with bather load in my pool I do refill and backwash what I'd say is more than normal. For winter when the chlorine demand is lower I plan on using bleach instead of cal-hypo.

My ongoing plan is to test the water daily and when the ppm has dropped by 1ppm I was going to add what I calculated to be a dose of 4oz of 73% cal-hypo to increase the ppm by approx 1 in 22k gallons of water. I may use liquid chlorine to shock the pool as necessary as opposed to cal-hypo.

-Tom
 
goodgnus,

obtaining and storing bleach to use as my primary chlorination method is a bit of a task
Click to expand...

:?: :?: :?: I don't understand.

You go buy 6% bleach at the grocery store or you buy 10% or 12.5% liquid chlorine at the pool store. Then you stick it in the garage. Where is the hard part of obtaining and storing come in?

I buy 6 cases of 2 gallon 10% at the local hardware store about every 5 weeks in the summer. In the winter this drops by at least a factor of 5.

Titanium
 

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Richard, or other chem knowledgeable folks.

I did read a case online last night where an individual was pre-dissolving cal hypo for multiple hours before pouring the liquid into the pool and leaving any white residue in the pre-dissolve container. Wondering what this white residue is? Undissolved calcium?
 
goodgnus said:
Richard, or other chem knowledgeable folks.

I did read a case online last night where an individual was pre-dissolving cal hypo for multiple hours before pouring the liquid into the pool and leaving any white residue in the pre-dissolve container. Wondering what this white residue is? Undissolved calcium?
Click to expand...

I would guess it's mostly Calcium Carbonate with possibly some Calcium Fluoride if the local tap water is fluorinated. Both are somewhat soluble in water. It would be easy to get a supersaturated solution by adding Calcium Hypochlorite to a bucket of water.
 
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