When does Chlorine level return to normal

Jun 24, 2011
Montgomery, AL
I shocked my pool last night after a large pool load and rainstorm. I brought the level up to 20 and am now wondering how long before the FC is at a level where swimmers can re-enter. It's Friday and the weekend is coming with hot days. What would be a good guess about normal FC level?


TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Feb 13, 2012
Phoenix, AZ
A few things:

shocking the pool is a process that often takes several days
normal (recommended) FC levels are 3-7ppm (but will vary based on CYA)
swimming at shock levels will be fine (so you are all set for the weekend)
FC retention will be affected by CYA level, direct sunlight, and bather load :mrgreen:


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Did you really shock? That's a process, not a one-time blast of chlorine.

I'm afraid the answer depends upon your CYA level. If it's 50 or above, you can go in right now. I'd suspect it will only take a couple hours to come down if you had a big load.

Just break out the test kit, see what CYA is and what FC is and compare it to this chart. If FC is below shock level for your CYA you're good to go.
Jun 24, 2011
Montgomery, AL
CYA is 40 and the target shock is 16, but I brought it up a bit higher just to be safe. The OCT held and it is coming down just trying to see how long. So they can swim at a level of 15? I suppose it will jut fade their suits a little and dry skin or no? I'll tell them it's okay. Thanks.

I think I'm going to bring my FC up above target level for a bit because we are supposed to get thunderstorms and heavy rain for the next week to week and a half.


LifeTime Supporter
May 4, 2011
I always add chlorine based on a guesstimate as to what tomorrow's weather will bring. The sun burns up much more chlorine than rain dilutes it.

Above normal usage I don't anticipate more than 1-1.5ppm during a storm.

Also - with the heat we've been having your FC levels might be low enough to swim by now.