Pool Math App FC levels for SWG differ from CYA/FC Chart


Well-known member
Sep 2, 2010
Montreal, QC, Canada
If you refer to CYA/FC SWG chart on the Troublefree site

FC on the chart has a range of between 3-5.

On the Pool Math application, the recommended range on the log page for FC using a SWG and a CYA of 70 shows a target range of between 3 and 10.

Which is the right one? I’m assuming the chart. Can the app be updated to reflect that?


Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
Southern OK
3 is the very minimum and you should never get to 3 FC, you should be targeting 5 FC or above to stay algae free... I keep mine between 6 and 7 FC at all times... You can go up to 10 and sometimes I do if I have my solar cover on and the FC does not get used as much..

I am down here in Oklahoma where UV kills my FC faster than you, I have my CYA at 80.. :)


Gold Supporter
May 20, 2020
Katy TX
Pool Size
Liquid Chlorine
We can ask @Leebo to confirm but the "target" is usually a range and not a specific number with the upper part of "target" is 15% of CYA value (approximately). So I think the that is how Pool Math puts in the target ranges.
On the CYA chart for CYA of 70 the 3 is the absolute minimum and the low range of the target is 5 with the high range of target calculated at 10 (15% of CYA 70). So the overall acceptable range is 3 to 10ppm but the ideal range is 5-10ppm.
FYI - the next higher value is SLAM which is 40% of CYA value. You can actually swim with FC up to SLAM value.
Hope this helps and others can provide their thoughts.
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