Just installed an IC40 but not sure what percentage to start with


New member
Jun 5, 2020
Tampa, Florida
I've recently started using a pentair IC40, today is day 3. I'm unsure what I should start the percentage of chlorine output. So I'm asking for a recommended starting point.
Here's my info and what I've done so far, excuse the long write-up. I have a 12.5k gallon pool with a VS pump that runs about 8-10 hours daily. I added 6 bags of salt to bring the level to 3600 and shocked the pool with 2.5 gallons of chlorine, the pool was a little greenish. Waited 24 hours and cleaned out the filter. I tested the water and was told salt is at 3600, to add 2 cups of acid and the chlorine level was a little high, as expected. I added the acid and an additive to clear up the cloudiness, called Pool First Aid by Natural Chemistry. It's been raining and expect more rain the next couple of days. I powered on the IC40 (day 1) and the display lit green stating levels were good. I set the chlorine output to 2% cause I didn't want to have too much chlorine in the pool. Day 2 I set the IC40 to 20%. This morning I see the pool is blue and clear. I intend to clean the filter again this weekend. Now that that's all done, what's a good point to have the percentage set until I test again? Should I test again today, out of that too soon?
Thank you!


Gold Supporter
Aug 6, 2019
Los Angeles, CA
Hello! I have an IC40 also, with an 18k gallon pool. To start with, recommend testing your chlorine twice a day while you get a sense of the different settings. If you have the PoolMath app, you can also see how much chlorine the IC40 will produce at different settings. It's under Chemical Addition->SWG I think.

As a rough point of reference, I set my IC40 to 50% and pump 32gpm when the cover is off. This roughly keeps pace with the chlorine loss from UV. I'll dial it down on a cloudy day or when I expect to leave the cover on for a long time. Right now it's set to 10%.

What are you using to test your water? Do you have an idea what your target FC/CYA levels are?


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

It is best to start high and adjust down, if needed..

I would start at 50%

I suspect that you have no clue what your FC (chlorine) level should be.. Without good test data you can't possibly know, unless you first know what your CYA (Stabilizer) level is..

This is because you must keep your FC in a direct relationship with your CYA, based upon this chart (see saltwater section) FC/CYA Chart

If you want to know more about our way of pool care, please take a look through our Pool School.


Jim R
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