Auto cover and FC loss


Gold Supporter
Jul 18, 2018
Canfield ohio
Usually I open my auto cover for at least 4 hours per day. But over the last two days due to me just not getting around to it it was not open and no one swam. Check out these numbers.

On Tuesday July 21 at 5:00pm my FC was 6.5. I had the SWG running at 50%. I did not lower it which I usually do when I cover the pool. This morning at 9:00am realizing I forgot to lower it I lowered it to 25%. At 4:00pm today I finally opened the cover and tested the pool. FC was 12.5.

So I started at 6.5. According to pool math and effects of adding over the 47 hour period from Tuesday to Thursday my SWG added 7ppm to the pool. That means I lost 1ppm FC over a 47 hour period.

That tells me a couple of things. My pool is clean and has no algae, no need for an OCLT test and the auto cover really saves chlorine use and will ultimately extend the life of my salt cell. But after two years of having a SWG with an auto cover you cannot set the SWG and just forget about it. You constantly have to adjust it based on pool use and the cover. I would be interested to hear from others who have a SWG and an auto cover on how they manage their pool.

I will now shut my SWG off and let my FC drift back down.

Thanks TFP.


Mod Squad
LifeTime Supporter
Jan 17, 2012
Evans, Georgia
Yup, I have that same thing happen at times. I tweak my SWG output % based on if the pool is open or shut for days on end.

You also save on not losing evaporated water!