General FC Question

[Kit]

I'm trying to figure out why the FC level in my in-ground spa is dropping. My IntelliChlor SWCG runs for 2 hours/day (@ 1800 rpms) with the output percentage set at 25%. The 2500-gallon spa is covered with an auto cover. Over the past week, I have added liquid chlorine to bump the FC level to 3 ppm. With each dose of liquid chlorine, I raised the SWCG output percentage incrementally from 10% to 25%. During this one-week period the spa has remained covered & unused. Yet the FC level drops from 3 ppm to 1 ppm every couple of days. I might add that the ambient temperature have been between 88F - 100F.

Although I could continue to increase the SWCG output percentage or the runtime, I wanted to check with those of you who are more knowledgeable than I. Ant thoughts on what might be causing the drop in the FC level would be most appreciated. Thank you kindly.

Kit

 

[jblizzle]

Turn off the SWG and run an OCLT ... that will tell you if there is something growing in the water consuming the FC which would required the SLAM process.

 

[Kit]

Will do & will report the results. Thank you.

 

[Kit]

I did the OCLT over an 8 1/2-hour period last night. The FC remained constant at 3.5 ppm. Any other thoughts on the dropping FC level? Thank you.

 

[jblizzle]

I am confused what do you mean by dropping the FC? Your FC is already on the low side usually the oclt is done in a much higher FC level.

 

[Kit]

I generally keep the FC level at 3-4 ppm. As indicated in my original post, with a daily runtime of 2 hours & the SWCG output set at 25%, the FC level still drops from 3 ppm to 1 ppm over a couple of days. The spa was covered & not used during this time. The ambient temp was between 88F & 104F.

I'm trying to determine why (in this situation) the FC level is dropping. Could the relatively high ambient temps in the past week be the culprit?

 

[jblizzle]

The SWG was off during the OCLT? Sounds like you just need to increase the output. Higher temperatures will lead to a higher FC usage

 

[Kit]

Yes, the SWVH was off. Increasing the SWCG output makes sense. Thank you.