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Post subject: Shelf Life for Liquid Chlorine
Posted: August 27th, 2007, 6:21 am
 Registered User

Joined: April 2nd, 2007, 6:38 am
Posts: 46
Hi,

Does anyone know what the shelf life is for liquid chlorine? Occasionally, Leslie's runs a sale on chlorine. Refill 2 jugs and get 1 for free. Instead of having the chlorine sitting inside my house go to waste, I rather pour it into the pool. Thanks.

Post subject:
Posted: August 27th, 2007, 8:09 am

Joined: May 7th, 2007, 3:03 pm
Posts: 29846
Location: Silver Spring, MD
Bleach shelf life depends on the concentration and the storage temperature. 6% bleach will keep for a year or two at under 80 degrees. 12% bleach will keep for a couple of months at under 80 degrees. As the temperature goes up the storage time goes down dramatically.

If you are getting 10% or 12% on sale one option is to dilute it one to one with water and store that.

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Post subject:
Posted: August 27th, 2007, 12:42 pm
 TFP Expert

Joined: March 28th, 2007, 2:40 pm
Posts: 8082
Location: San Rafael, CA USA
The table at the bottom of this link gives some half-life numbers for chlorine at various concentrations and storage temperatures. The half-life is how long it takes for the chlorine to lose half of its strength. Most of the strength is lost earlier on as this is a non-linear process (it's an exponential decay whose rate is faster at higher concentrations).

I use 12.5% chlorinating liquid and find that it keeps nearly all of its strength over a month, but the storage temperature is from 60 (night) - 80 (day) degrees, typically.

Jason's suggestion of diluting the chlorinating liquid for longer-term storage is, of course, excellent. Just be sure to dilute with relatively pure water that does not contain metals. So most city water is OK, but well water is most likely not and could accelerate degradation (metals act as catalysts to speed up the degradation process).

Post subject:
Posted: August 28th, 2007, 12:35 am

Joined: April 21st, 2007, 11:49 pm
Posts: 925
Location: Arizona
Something I have noticed and I would think would surely affect this is that the off brands usually have a seal you must peel off, under the cap - which I'd think is a good idea. While the Chlorox brand does not have this type of seal. The bottles I purchase of 12% fresh chlorine don't have it either and they told me, at the store I purchase them from that I shouldn't stock up on them because they can lose quite a bit of potency in a couple of weeks. Of course the temperature here is in the 100's this time of year, too.

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Post subject: Re: Shelf Life for Liquid Chlorine
Posted: August 28th, 2007, 5:57 pm
 TFP Expert

Joined: March 29th, 2007, 11:56 am
Posts: 4160
Location: Coastalish 'down easter'
rainman168 wrote:
Hi,

Does anyone know what the shelf life is for liquid chlorine? Occasionally, Leslie's runs a sale on chlorine. Refill 2 jugs and get 1 for free. Instead of having the chlorine sitting inside my house go to waste, I rather pour it into the pool. Thanks.

What makes you think I don't want it?

The above advice is great, just keep it at a fairly ~ neutral temp and out of direct UV exposure

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Post subject:
Posted: August 31st, 2007, 2:07 pm

Joined: August 9th, 2007, 9:21 pm
Posts: 9
Location: Hemet, California
JasonLion wrote:
Bleach shelf life depends on the concentration and the storage temperature. 6% bleach will keep for a year or two at under 80 degrees. 12% bleach will keep for a couple of months at under 80 degrees. As the temperature goes up the storage time goes down dramatically.

If you are getting 10% or 12% on sale one option is to dilute it one to one with water and store that.

Does anyone know if this works -- has it been tested?

chem geek wrote:
The table at the bottom of this link gives some half-life numbers for chlorine at various concentrations and storage temperatures.

The table that chem geek references shows that at a given storage temperature the half-life of bleach is a function of the
manufactured concentration. For example, at 80oF 10% (trade %) bleach has a half-life of 241 days while 5% bleach has a half-life of 735 days. If I buy 10% bleach and store it for 241 days it will have a chlorine concentration of 5%. But it will not be the same as bleach manufactured at 5% -- it will still have a half-life of only 241 days. I don't know what causes the difference (maybe accumulated chlorates or different amounts of metal ions introduced in the manufacturing process or something else). In any case, I can have two bottles of bleach with the same concentration of available chlorine but with two very different half-life's.

I can't deduce from this information what the half-life would be if I were to dilute 10% bleach to 5%.
Diluting bleach is not a fun job and I don't think I'd be willing to do it without more evidence that I'd be gaining half-life.

So, is there more information available? Or has someone on this forum actually done this and measured the results?

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Post subject:
Posted: August 31st, 2007, 2:22 pm

Joined: May 14th, 2007, 8:30 pm
Posts: 375
I know most bleaches come without a sealed top,would them having a sealed top effect the shelf life?

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Post subject:
Posted: August 31st, 2007, 2:52 pm

Joined: May 7th, 2007, 3:03 pm
Posts: 29846
Location: Silver Spring, MD
It is very imporant that you don't add any metals to your bleach. It wouldn't be a good idea to dilute bleach with well water high in metals.

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Post subject:
Posted: August 31st, 2007, 3:10 pm
 TFP Expert

Joined: March 28th, 2007, 2:40 pm
Posts: 8082
Location: San Rafael, CA USA
It's more the other way around. If well sealed, the bleach will not have additional loss from exposure to air and mostly from outgassing.

The bleach (in the discussions in previous posts) degrades because it is concentrated, not because it is escaping. It's just a natural chemical reaction since chlorine is by its vary nature unstable -- that's what makes it react with many chemicals and gives it its power to oxidize and to kill pathogens. So not only does sunlight breakdown chlorine, but chlorine can react with itself to break itself down and this is what happens fast enough to notice when the chlorine is more concentrated. It's also why the rate of breakdown varies roughly with the square of the concentration so that 12.5% chlorinating liquid breaks down about 4 times faster than 6% bleach.

Higher temperatures accelerate all chemical reactions so increase the rate of breakdown of chlorine as well.

Richard

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