Time of Day to add Chlorine


May 21, 2019
Austin, TX
Moved from here.

My CYA is almost at my "summer level" of 60. My May vacation is when I use pucks and it does double duty to raise my number as well as chlorinate while I'm gone. Keep yours around 60. Think of it as SPF for your chlorine. Makes it last longer and can do it's job better! I use about 1/3 gallon of chlorine per day (depending on % it can be
more or less). My pool is partly shaded too and about your size. Just pick up a few bottles of regular unscented, no polymer bleach or their Pool Essentials Liquid Chlorine (higher %) when you stroll through Walmart. HD or Lowes carries liquid chlorine too. It's less work than you think and the rewards of a TFP with spectacular water is worth it!
Does it matter what time of day you add liquid chlorine? In my head it makes more sense to add in the evening so the sun doesn't burn it all off but if I have good CYA levels does that even matter?
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Gold Supporter
Jun 13, 2017
Rochester, MN
I like to add at night. Just seems to me it's a good idea to give the chlorine a chance to work on any nasties without the sun burning it off. Of course, if I think there might be nasties, I'll also test in the morning to make sure too much didn't get consumed over night.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
All that really matters is that the pump runs at least half an hour after to mix it all.

Lets say minimum is 4 and target is 7. It matters not if it goes to 7 at noon, drops to 5 by dark, stays at 5 all night, and dips to 4 by noon or if it goes to 7 at 10 PM, stays there all night long, and drops to 4 by 10 PM again. Same amount added, same amount lost, never dipped below minimum.


Gold Supporter
Jun 13, 2017
Rochester, MN
Richard, that makes so much sense. The key is staying above the minimum.

Everyone's schedule is different. For my schedule, making sure I'm at a good FC level each night just the easiest.


Bronze Supporter
Nov 12, 2016
Plano, Texas
For me, it's usually early evening when the sun is off the pool. Depending on my schedule, sometimes it gets added in the morning. I don't worry about when it goes in as long as I'm testing when I should and adjust as needed.