Chlorine Date Code Decoder/Easy Way to Measure Strength.

epro05

Bronze Supporter
Jun 5, 2014
275
Keller, Texas
#1
Hi, I just joined TFP this season and pool is looking great. TFP is an awesome resource. Thanks

I thought the information below might be helpful for some of the forum participants.
I recently bought 1 jug of 10% Liquid Chlorine that was actually 4.5%. It had a 2013 date code. I now am very careful to check the date code before I purchase.

I thought this might be a handy reference for checking bleach/liquid chlorine date codes. This decoder is for the brands that are available in my area. If you have other brands please add to this thread if you want.

Note: Further down I show an easy way to measure the strength of your bleach/liquid chlorine.

Bleach/Liquid Chlorine starts decomposing after it is manufactured. Check this link (scroll down) to see the half-life table (half-life means half of the original strength). Note that decomposition occurs faster for higher strength chlorine and faster at higher storage temperatures.


Bleach/Liquid Chlorine Date Code Decoder (Year/Day of Year)

Here is a Julian Date chart.

Clorox
A5 3 183 TX-1 08:41 (Day 183 of 2013)

Walmart Great Value
14 183 11:03 B1

Walmart White Cloud
14 144 12L59 B2 TX-01

Smart (Home Depot)
34713FL07:30

HTH Liquid Chlorinator
14JA0366B 11:15

Kem-Tek
1416210:25C

Dollar General
14 169 02:59 B2 TX-01

Online Packaging Inc
BB 07/01/15 (Date of Manufacture is 1 year prior to the "Best By:" date.) In this case Manufactured date is 07/01/2014.



Easy way to measure strength of bleach/liquid chlorine.

A 10,000 to 1 dilution of chlorine will result in chlorine ppm equal to its strength (percent). All you need to do is to make the 10,000 to 1 dilution, then measure the ppm using a FAS-DPD test kit. Example: If the dilution measures 8.5ppm, then your bleach strength is 8.5%.

Step 1: Measure 1 liter of Deionized or Distilled water. Here I’m measuring 1000 grams (1 liter) of water using a kitchen scale.



Step 2: Measure 0.1 ml of the bleach/liquid chlorine. This is easy to do by using a 0.3 ml u-100 insulin syringe and filling it to the 10 units mark (10 units of u-100 insulin is 0.1 ml)




Step 3: Add the 0.1 ml of bleach to the 1 liter of water and mix.

Step 4: Using a FAS-DPD test kit, measure the FC ppm (CC should be zero) of the dilution. The measured ppm is the percent strength of your bleach/liquid chlorine.

Hope this is helpful to some.
 
Last edited:

easttn

Well-known member
Jun 22, 2013
309
East TN
#2
Thats some interesting information. Instead of going through all that trouble, why not measure your FC level then put 3ppm chlorine in the pool and wait a little bit, then check to see how much your FC has risen. This would be a little more accurate when the sun goes down of course and wouldnt work if you have algae or other problems.
 
OP
OP
epro05

epro05

Bronze Supporter
Jun 5, 2014
275
Keller, Texas
#3
You're right. I could do it that way too. But as you mentioned, the dilution test does eliminate the other variables (algae or other problems). I've seen several posts where members say that chlorine disappears as fast as they add it, have excessive loss, etc. Independently checking the bleach strength just seems like a good idea to me, just to make sure the chlorine is not disappearing because it wasn't there to begin with.
 

Big Splash

LifeTime Supporter
Jun 2, 2014
40
New Jersey
#4
Interesting. Correct me if I'm wrong, but the kitchen scale is measuring by weight where as the syringe is measuring by volume right? So, would they be the same proportionally?
 

JVTrain

TFP Expert
Feb 3, 2014
5,080
Central Minnesota
#10
I'm unsure on what the date code on the liquid pool shock, 12.5% that I buy at Fleet Farm means.

The code on my current bottles reads: WI-1 1440
The next line reads: BB 07/01/15
The outside of the cardboard box that holds the 4 jugs says SWIM SHOCK 12.5% JY

Obviously the second line is best by the date listed but that doesn't mean much. The product is manufactured in Wisconsin so I am assuming the WI-1 has to do with it was made at the Wisconsin location, perhaps 1 being a specific line of equipment in the plant? the 1440 could mean the 40th day of 2014, which would be February 9th but then the best by date doesn't make much sense unless they have a 17 month best by criteria. I may call the manufacturer, OnLine Packaging, Inc. to see if they'll give me an answer about the date code. They JY on the outside of the box simply points to the July best by date, I would presume.

Update: Found older bottle in the recycling bin. This one has WI-1 1226, BB 06/03/15. Box in came in is long gone in a campfire... Then the 1226, 1440 don't make sense for year/day. Safest assumption is best by date is 1 year from production date.
 

Thehobe

Active member
Sep 22, 2014
29
Los Altos, CA
#13
OK, love the info but I just bought HTH 10% from Wallmart and the only stamping on the box is "C2274" as the lot number. Is there any way to figure out the age from this lot number?
I would measure it in an instant with the test method but where do I get an insulin syringe?

Also, once you put bleach into the pool does not some of it immediately combine with CYA? I have high CYA levels and cannot get my FC up and stay there.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
41,197
Tucson, AZ
#14
You misunderstand the way FC and CYA work. You must maintain proper FC levels for your CYA level ... The CYA will not make the FC read lower.

If you can not maintain FC levelsand have high CYA, you likely have algae in they pool and need to SLAM.
 

Thehobe

Active member
Sep 22, 2014
29
Los Altos, CA
#15
I describe a way to measure purchased (aged) Chlorine with a simple test kit if you do not have a syringe as described above:

Take a used up OTO 1/2oz empty container, wash it out with distilled water several times. (you can pop out the eyedropper from these bottles).
Fill the bottle to the brim with your specimen chlorine and put back the eyedropper top. The bottle (1/2 oz. stated will actually contain 300 drops and/or 2/3 oz. of chlorine)
Fill a gallon milk jug or used liquid chlorine container with distilled water, making sure to fully rinse out the container several times (or buy a gallon of distilled water).
Now put 1 drop of the chlorine specimen into the gallon jug and shake/mix thoroughly. Measure the mixture in your normal test kit way with the OTO solution.
Because the mixture is {(1 drop)/(300 drops)x(2/3 oz.)}/128oz. or 17.5ppm of chlorine solution, if you have 10% solution you should measure 1.75ppm from your test kit.
If you are using 8.5% chlorine, then you should measure 1.5ppm and for a 12% chlorine solution you should measure 2.1ppm chlorine.

I know this is only approximate depending upon the OTO test kit color recognition, but at least it will tell you how potent, roughly, your chlorine specimen is.

You may do better with a DPD test kit using titration.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
41,197
Tucson, AZ
#18
Should work. The idea is for the extra water to not have any chlorine or CC in it like tap water usually does.

Although in reality, there is not much point to doing this test as the errors can be pretty large.