Testing the strength of 12.5% chlorine

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
It takes some pretty accurate equipment to get an accurate test of strength of the bleach.

You can use the pool calc if the 6% has been pretty accurate in the past. 12.5% should take half as much to raise it the same amount.


LifeTime Supporter
Apr 12, 2011
Brookeland, Texas
Couldn't use the pool calculator to figure the amount to use in a known smaller volume of water, say 5 or 10 gallons, add that amount to figure the strength based on FC rise.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
1/4 teaspoon of 6% bleach in 2 gallons of chlorine-free (and chlorine-demand-free) water is 10 ppm FC. 1/4 teaspoon of 12.5% chlorinating liquid in 2 gallons is 20.4 ppm FC so 1/8th teaspoon is 10.2 ppm FC.

If you have a spare Taylor or TFTestkits bottle from one of the reagents (especially the titrating ones), then they are 24 drops per ml so 24 drops is 1/5th teaspoons. 1/4 teaspoon is about 30 drops. 1/8th teaspoon is around 15 drops.