How to read production date of SH

Been scanning the threads for the past 2 hours roughly and can’t find the answer to the following question. How do I determine the expiration date of a bottle of SH? I’ve been running Clorox Outdoor bleach, but after being on this forum for a few weeks, and being a good young grasshopper, I know now that I need to do better with better. A local guy on this forum reached out to me and offered me some of his good 12.5% SH when he makes a bulk purchase, but if I ever get in a bind and need some of the 10% that wally-world sells how do I decipher this this date stamp?

I don’t know that there is an expiration date. SH degrades over time according to environmental factors. There are chemical test kits to test the strength but it’s time consuming and unnecessary. Usually you can tell if it’s strong enough by smell or testing it on something. Also, the old stick your finger in it and see if it turns your skin white and feels warm/hot will indicate strength.


Most sh will stabilize around 6 percent one way or the other. When it reaches 6 % it will stay there for years

Not that its 100% applicable to this but many in the prepper community considers 6month old bleach to be unreliable for water purification.

More a rule of thumb than a true rule.

I remember someone telling us on here not to long ago how to read those dates. The only way I can make sense of that would be
19 = year
354 = 354th day of the year (Dec 20th)
Again, that’s just a guess.


You sir are correct. I was the one who told y’all how to read it. 354th day of 2019. That is the production date


Ok so not to derail this but you are telling me that if the zombie apocalypse or what reason you are prepping happens that you would discard all your sh after 6 months or at the very least stop using it for water purification

@Crystal-Clean, @Max1, that’s what I was looking for, so thanks y’all! I had been able to see in one of the previous threads on SH breakdown that the resident chemist had uploaded a PDF showing breakdown of SH over time, with the various variables that can come into play, but I didn’t know how to determine how fresh a bottle would be on the shelf. Kind of like buying milk, I’ve always scanned the grocery store cooler for the furthest out expiration date. Wal-Mart had this SH on the shelf today and it made me wonder if it was “fresh” or possibly leftover from last summer. Thanks everyone!

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The stronger it is the faster it breaks down. SH will continually break down until it reaches it base components. How long? I read everything I could, Spec sheets, research reports, journal articles, etc. there is no one definitive answer that I have found. Having said all of that, if the bottle says 10% it is very likely that when it was bottled at the factory it was probably bottled at a higher percentage. The research and articles I read indicated that many places were actually bottling 15% then shipping it out labeled as 12.5%. The companies were worried about summer heat, transportation length, and length of storage breaking it down prior to arrival at it’s destination.

Having said all of this, do your own due diligence.


Sh never gets old, only degrades in strength. Whatever you have lying around the shop/garage is great pre treatment no matter how old. Thers always a use for sh that’s been sitting around.


Even under ideal conditions, the amount of available chlorine will decrease over time. The Chlorine Institute has developed a formula for estimating the concentration of material stored at 80 F with an original available chlorine concentration of 13%:

0 13.00 %
30 10.95 %
45 10.05 %
60 9.23 %
75 8.47

Here is a breakdown estimate for your perusing Cut copy and pasted from the PDF i downloaded. Just so no one thinks I am making stuff up.


Does that include sitting in a batch tank or just the bottles?

Thank you all. I’m realizing that I was misleading with the tag line on this thread. I should have titled it “production date of SH”.

I changed it for ya

Thanks @Crystal-Clean !

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@CaCO3Girl would be the best source of info on the lifetime of SH, if she’ll weigh in on this, that is.

Would you mind posting the link for the pdf you mentioned? @Dirtyboy

Nope, but they dont store the liquid kind, they store powdered and make up concentrate as needed. Again totally off thread.

I tried to upload the pdf but this site won’t let me. I believe that this is the place where I got it from, but this is one of many documents I have in my chemical file. Water System Chemicals, Filter Additives | Wilson, NC

I believe that this company is in your neck of the woods so to speak.

Thanks for the link. I’ll try to find it and see if I can post it somehow.