Bleach Addition: Day or Night?


Well-known member
May 22, 2016
I have been following TFP practices for a while and still learning. Gotta question: excluding OCLT tests, when you add bleach say daily in the summertime as required to keep FC in recommended range, do you add in morning or night? And does it matter? I ask bcos I am a morning person and prefer to add bleach in the morning. My DW on the other hand thinks it’s “better” to add at night. Thoughts? Pros/Cons?


Mod Squad
LifeTime Supporter
TFP Expert
Apr 18, 2010
East Texas
If you add in the am to raise to burns off all day and sits there all night with lower FC. Evening is best.


Mod Squad
LifeTime Supporter
TFP Expert
May 19, 2010
Tucson, AZ
Does not really matter.

There may be slight advantages to doing it in the evening ... longer period at higher FC to work on anything in the pool when no sun to break the FC down.
But, since we do not expect much of any loss over night, your FC will still all be exposed to the sun eventually.
I would guess the amount you have to add would not change regardless of when you test and add it.


Gold Supporter
Mar 11, 2018
Texas City TX
I personally add morning (7 ish) and evening 5-6 ish. I check FC twice a day, until I get a good feel for this method and what this SE Texas heat will do to my FC. The Poolmath app is a great help.


LifeTime Supporter
Aug 19, 2014
Pacific NW
I typically add in the evening Tue after work and Saturday after I swim or guests come over.

That's when it usually needs a top up.
I like to add at night so it’s at a higher level for longer. Also, my pool gets used mostly in the afternoon and adding the chlorine at night puts the chlorine in the water sooner after it was used to kill any “kid stuff”.
To be honest since the FC is always above the minimum value, it shouldn’t matter either way.