Maintaining Pool since summer (new Pool) and suddenly FC is really high.


Well-known member
Jun 2, 2019
Florida, USA
Hi. I've been doing my own maintenance and using the TF100 kits and my FC level has been between 4 and 10. 15 days ago was @ 8 using the DPD R-0870 Powder. From there it went to FC of 10 5-days ago.. I had a little DPD R0870 and it was way black so I decided to order a new one. It came today in the mail and re-test today and FC came @ 16. SWG is at the same percent for months (40%). Nothing has changed. I will take all measures on Saturday. I did took PH today and it was above 8 but I read that with FC above 10, measuring PH is not accurate.

We are having chilly weather here down in FL but not sure if my readings are normal for that weather. I also did the the FC/PH test using the K1000 Basic OTO test and the color for the FC was way orange to compare with the yellow I'm suppose to have.

5 days ago my readings were:
FC 10 (With DPD R-0870)
PH 7.8
TA 70
CH 350

CYA 70 (Back in October 5)

I'll be leaving out of town next week for 7-8 days. I'll be taking new readings on Saturday.

Any feedback.
Last edited:

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
It is possible the old powder was simply bad. Black in color for the R-0870 is not good, so the new numbers seem to be more reliable. In addition, cooler weather usually means cooler water. Together that means FC will not get used as much, and if your SWG is cranking-out the same amount of FC, it will continue to climb. Might be nice to know your water temp.

Either way, it sounds like the SWG % and/or pump run time should be dialed-down just a bit to let the FC fall. Yes, the pH number is skewed at the moment, so you'll have to wait until the pH gets back to 10 before validating.


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

SWCG's are in an open loop system, they get no feedback, they have no clue what the FC is. They just make the amount of chlorine you tell them to make. You have to be their brain... You have to test, determine the FC is not correct, and then turn the % up or down to make the FC do what you want..

This time a year the sun is at a different angles and will consume less FC. It is quite normal for SWCG owners to reduce their outputs to single digits this time of year.


Jim R.
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LifeTime Supporter
Sep 15, 2012
Don't be surprised if you end up having to set the SWG much lower than 20% with a water temp of 63. As others have suggested cold water + shorter days can significantly reduce chlorine demand.