How to determine the strength of your bleach?

[Her pool boy]

Hi. Have a bit of a head scratcher. I added enough bleach last night, according to pool math to raise my FC by 2. But It only ended up raising the FC by 1. My FC was 2 and 90 minutes after adding it measured 3. I measured again this morning and got 3. I know bleach loses strength over time, I am just wondering if there is a way to measure the strength of the bleach.

I am am also pondering whether whenI measure 3 last night The chlorine hadn't mixed completely, and it got to 4 overnight and lost 1 FC before I measure this morning but don't think that is likely because I haven't been losing 1 FC over night.

i suspect bleach strength but don't want to assume anything, then over chlorinate. Is there a way to test? that is the question..

Readings this morning are

FC 3
CC 0
pH 7.6
TA 100
CH 150
CYA 35

 

[Mr Bruce]

I did a bathtub test one time. Seemed to work pretty well. I used the bath tub and pool math to calculate bleach strength

 

[woodyp]

Commercial bleach: testing concentration

Happy reading!

 

[JVTrain]

Two options.

See the directions in this post: Commercial bleach: testing concentration

Or... Taylor has a test kit to test the strength of bleach. Welcome to Taylor Technologies Not sure its worth $100 to you though.

 

[Her pool boy]

The reading links were very helpful, I think I like the chem geek's method, and based on that my bleach is currently at half strength.

 

[phenol red]

Keep in mind that bleach decomposition rates can be predicted:

Breakdown of bleach over time by storage temperature - Page 2

 

[Her pool boy]

Thanks red...it now all makes perfect sense.