Beware! Math on liquid Chlor. % from pool store.

[geoshecks]

Hi everyone,

I purchased some liquid chlor in in a 5 gallon container from the pool store. At 16.99 for 5gal., it seemed a good deal esp. for ease of handling.
After learning that the 12.5 degrades quickly, I wondered about the age of what I bought. So I did the math. Someone please correct me if you think I'm wrong.

I used new graduated syringes and a graduated beaker.
I diluted the bleach first by 5ml per 500ml=100:1
Then I did the same with that solution 100:1
Which means the original chlor is now diluted 10,000 to one.
The tf 100 showed a FC of 7.5 ppm.or .0000075%
times the origional dilution of 10,000:1 = .075 or 7.5%

So the liquid chlorine seems to be weaker than advertised. This seems to be reinforced by my test of the pool water 1 hour after adding this chlorine in the evening. I used the pool calculator to determine proper amount to raise the FC to 15ppm. I used a graduated cylinder to accurately measure the liquid chlor. My testing revealed only 11ppm.

I know this seems like overkill, but I had to satisfy my curiosity. I think the pool store most likely carries this stock over year to year.

My conclusion:
The price and convenience may seem attractive, but stick to A store that turns the inventory quickly such as Walmart, etc.

Someone please correct me if my method and calculations are wrong.

O.K. now everyone, I may have put you to sleep so, WAKE UP!

 

[JasonLion]

Yes, a 10,000 to 1 dilution is what you want. The dilution is easy to get wrong, you need to be especially careful to avoid any contamination of the high strength original into the second dilution, but if you are methodical it can work well.

 

[gtm]

Just a couple of thoughts ...

First, I have a pretty good PS for my chlorine, but I have noticed that sometimes it seems a little weak, in the sense that I have to add more than expected based on my normal usage. I've also noticed that this happened more during the winter (in FL where we don't close) when they weren't turning it over as quickly. So my experience supports the idea that you need to think about how often they sell it; i.e., keeping it from "year to year" is likely a problem.

Second, some people here have said that the best way to test chlorine is to see how much it raises your pool's ppm, as the OP did. With a round pool and a decent estimate of the depth, you have an excellent measure of the volume, so that test is likely more accurate than the dilution test assuming that you don't have an organics problem. This, BTW, is how I checked the volume estimate on my pool! I think duraleigh suggested that, but I'm not sure that I'm remembering the old posts correctly.

 

[Guest]

If you are going to buy liquid chlorine try to find a store that sells it in either 2.5 or 5 gallon refillable carboys. They will have a storage tank for the chlorine on premises and it means that they sell a lot of the stuff so it should be fresh! The stuff in gallon jugs could have been sitting in a warehouse for who knows how long under who knows what type of conditions before it even made it to the store! If you are going to buy gallons, then regular laundry bleach has a better shelf life and the outdated stock usually ends up in the dollar stores so don't buy it from there!

 

[? D ?]

My conclusion:
The price and convenience may seem attractive, but stick to A store that turns the inventory quickly such as Walmart, etc.

I'm happy to follow that conclusion

 

[geoshecks]

These were the 5 gal. carboys, but they were filled off premises. Maryland hazmat laws are very strict apparently. Most people do'nt know it's the same stuff, so 1gal. jugs are more popular.