In July 2014 I bought a house in Spring Hill Florida (same latitude as Orlando but 9 miles from Gulf) with a pool (my first).
Since then I have had a recurring problem with yellow-green "dust" on the pool floor and sides. I call it dust since it swirls up like dust when gently brushed. It does not disappear. I shocked the pool once (before finding TFP) and have slammed it several times with varying degrees of success but the problem has always recurred. Sometimes the pool gets very green and sometimes the color only changes a little. The pool has a 90 sq. ft. cartridge filter, with a spare cartridge, which sometimes clogs enough to reduce suction to almost nothing while sweeping the pool. When washing a cartridge I get yellow-green water and can see green on the dirty filter. Is this an algae problem and is it likely to be "mustard" algae?
The next to last slam I used the pool math mustard slam levels for chlorine. The last time I used the Chlorine/CYA Chart by Chemgeek mustard levels and kept level above Yellow/mustard min. (except last day when problem had already returned). Both times I swept each day and changed the cartridge at least once, twice if it reduced suction during sweep. Both cartridges were soaked in TSP around October. The pool has an underwater light which I removed last time and there was a small pile of yellow "powder" under the light. I removed the light a couple of days ago and there was nothing noticeable. It is still out and will remain out until the slam is finished.
I have put all the tools and toys used in the pool in the pool during the slam for several hours and all pool clothing has been laundered several times. Make up water is from the public water supply.
I am in the process of slamming it again.
The pool is heated and is kept between 81 & 83 F. I have a 12 mil solar cover which is on the pool except during pool use or slamming. The cover came with a statement that it should only be used with a cholorine level of 4ppm (not sure of exact number but low) or less. What does higher chlorine do to a cover? I have put the cover on today as it seems to me that it needs to be slammed also.
The pool is screened and there is significant yellow-green on some of the screens. I assumed that this was pollen, probably pine, which I was used to from NH and which I have been told is a significant issue here in Spring Hll. Does that have any bearing on this problem?
The slamming instructions say to test the pool hourly. Is an hour really long enough for a chlorine addition to thoroughly propagate through the pool? When I started this slam I was trying to raise FC by 15ppm. after 2 hours it had gone up 8.5 ppm. In another hour with no additional chlorine it had gone up another 3 ppm at which time I added more chlorine thinking that some had probably been used up by then.
Test Results last few days using TF100 test kit.
1/18 10 AM FC 7, CC not checked, TA 110, CYA 30, pH 7.f, ch 275. Added 3lbs 8oz Calcium Chloride.
1/19 6 PM FC 6.5, CH 300 others unchanged
1/23 1:30 PM FC 4.5, CC .5, CH 300, TA 110, CYA 30 Added 2.25 gallons 10% liquid chlorine
1/23 3:30 PM FC 12.5
1/23 6:00 PM FC 14.5 Added 3qts 10% liquid chlorine
1/24 7:45 AM FC 17 Added 1.5 qt 10% liquid chlorine