How much should my chlorine level drop a day? And strange yellow spots.

TigerGalLE

Member
Jun 10, 2020
14
Upstate South Carolina
So I super chlorinated my pool right before going out of town using my SWG (18k gallon salt water fiberglass pool). Then I left It to run for 11 hrs a day at 40%. I was gone 5 days. When I got home yesterday my FC was still 13.5. I turned my chlorine generator to 0% and today it was 11.5 at the end of the day. Water temp is 80 and full sunshine today. Is this good? Normal? Expected?

I also have seen some yellow circles stuck to my stairs. It won’t vacuum off but brushes off easily. When I looked at it with my goggles it had a gritty texture. Is this algae? Or something else strange?
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
So it appears you lost about 2 ppm of FC in 24 hours correct? If so, that's fine. It's when the FC demand exceeds 4 ppm without good cause (i.e. swim party) that we get concerned. Also, since you have a salt pool, ensuring your CYA is adequate (usually about 70 ppm) to protect the FC is important as well.

As for the yellow circles, I thought maybe pollen, but you said it was gritty. Do you have a sand filter? Your signature does not specify.
 

TigerGalLE

Member
Jun 10, 2020
14
Upstate South Carolina
I do have a sand filter. We also have some exposed areas of dirt around the pool that the grass hasn’t grown all the way in. Sand does get in the pool at times from dirty feet but that vacuums right up.

I saw more spots today. They don’t vacuum off but I can brush them with my hand. It is really strange.