Heavy rain earlier....do I need to shock? *TF-100 results included!*


Bronze Supporter
Dec 24, 2018
Columbus, OH
I’ve had my pool up since the end of July and have yet to “shock” it because for the most part I’ve been keeping the chemicals balanced (alkalinity is super high always so far and my pH is usually perfect but today it is high). FC, CC, TC, and CYA are great and I’ve never had cloudy water; only crystal clear.

Now this post isn’t to brag lol. I’m wondering if or should I should shock my pool since it’s already been through 2 heavy rains in the past 7 days? There is debris from the storm earlier and I tried to remove as much as I could before I can vacuum (I need hubby’s help lol don’t ask). I’ve never seen even a sign of algae *knock on wood* but have read that I should shock after heavy rains.

I tested my water this morning with my TF-100 kit. Results are in the screenshot below...


Soooooo pool experts, should I shock or continue what I’m doing? And yes I’m working on the pH and alkalinity lol. My pH decreaser will be arriving tomorrow! I run my pump 8-9 hours a day every day. To shock or not to shock? That is the question lol. Thanks in advance!!


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

Rain does not cause algae as many assume... What it will do, however, is dilute your FC.. If you run close to your target FC level, then this should not be an issue.. But some have this fear about chlorine and try to run as low as possible... These people often don't realize that after a rain storm that their FC has dropped too low...

If my target was 3 to 7 I would be running at 6 or 7... Running at 3.5 is just way to low for my taste..

It makes sense to me that if you are worried, just measure your FC and bring it up to your target level if needed.


Jim R.
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