Which chlorine test to use daily in tf-100 kit


Well-known member
May 21, 2010
I have been using the drop test with the powder everynight to check my Fc. After reading instructions it says you should do that test once a week and use the OTO one daily. After seeing how much of the powder I have and how much it cost im thinking I shouldnt use it as much or will be out fast. I have a hard time telling the colors apart on the yellow OTO test. I pretty much add the same amount of bleach a night so If I go over a little I should be ok. How do you all test everynight?


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
I use the powder and drops. I don't really have a choice, as I am stuck with high CYA until water restrictions are lifted or I spring for reverse osmosis. I keep FC at about 15, where the color matching test is useless. I only test every 2 or 3 days right now. With things warming up, and actually using the pool, I may have to go daily.


Well-known member
Feb 18, 2010
Houston, TX
Well, my pool isn't up yet, but I do use the kit for testing my hot tub. Since that's sort of a different beast, I use the powder and drops every day. When we start using the pool, I plan on doing the OTO every day and the other probably every 3rd day, until I get a feel for what the pool needs.


LifeTime Supporter
Jan 11, 2009
Cupertino, CA
What cheddar85 said is pretty common; as you get to know your pool, you can use the OTO test for a quick check and once or twice a week use FAS-DPD to really nail a number.

Some people have real trouble reading the OTO test and distinguishing the shades of yellow, and so use FAS-DPD all the time. It does cost more that way. One thing to try is to run both tests for a while, and try to "train" your eye to associate a certain number with a certain shade of yellow.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
The kit was designed so that you deal with problems and figure out the correct amount of chlorine to add day to day using the FAS-DPD kit. Then when things are going smoothly you use the OTO test just to make sure that nothing has gone wildly wrong. While using FAS-DPD weekly to see if you need to fine tune the amount of chlorine you need to add. Not everyone does it that way, many people use FAS-DPD every day.

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