Question on my first SLAM

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btmansfi

Active member
May 5, 2015
40
Chesapeake, VA
So I opened our pool about a month ago. Lately I've been seeing little areas in the corners of the pool on the floor that look like sand/dirt. When you brush them they dissipate and later come back. Appears it's mustard algae.

So yesterday afternoon I bought 12 gallons of 8.25% bleach (121 oz each). Before putting anything in the pool my CYA was 45-50 and FC was 0. Here's a list of my steps:

SWG OFF, filter on
5/7 7:00PM added 6 gallons of bleach; brushed pool
5/7 8:00PM FC=25, CC=1
5/7 9:30PM FC=23.5, CC=0.5

5/8 6:00AM brushed pool and vacuumed up mustard algae
5/8 6:00AM FC=22.5, CC=0.5, then turned SWG on at 100% and went to work
5/8 6:00PM FC=16, CC=0.5, still had some algae in the pool so I brushed and vacuumed again

What I don't get is how overnight I lost very little FC and my CC was under 1. I left the house this morning with FC at 22.5 AND my SWG on 100% all day. How could I come home and FC be less than when I left? I understand the sun dissolves some of it, but it was fairly cloudy today. I find it hard to believe that my FC would drop 6.5ppm while the SWG was also running at 100%. That means I probably really lost 8-9ppm FC during the day today. But what throws me off is that CC is still basically 0.

Should I add more bleach?
 
Don't run your SWG during SLAM. You can have 0 CC and still have something going on. Just keep adding bleach to shock level until you pass OLCT, your pool is crystal clear and your CC is 0 which you already have. When adding in the morning overshoot your FC shock level since you don't add again until evening. I would overshoot it by 4-5 ppm tomorrow and see what happens.

- - - Updated - - -

Also it am not so sure it is mustard algae. How does your water look right now? It could be pollen or may just be sand too
 
Sunlight uses some of that FC. And algae grows in sunlight, so there is more to kill off during the day, which uses more chlorine. You still see some, so it's growing. SOunds normal to me, Keep the FC up and keep brushing. You need to disturb the slimy scab the algae grows to protect itself so the chlorine can get in there and kill it. And do not neglect ladders and steps and lights. They provide good hiding places.
 
So after passing the OCLT, what's next? If tomorrow morning my FC is unchanged at 22ppm (I added a gallon of bleach a little while ago), water is clear, and CC is 0 will FC gradually just make its way down to somewhere near 5 and level off? Just trying to think how that will be possible if I have my SWG going and assuming that negates the lost FC due to sun. Should I not run my SWG until FC comes back down to closer to 5-7?
 
MarianParoo said:
Great. Retesting after additions on an OCLT is often overlooked. Good job, and good luck!
Click to expand...

Or any add in the beginning of the SLAM when you are not sure if your bleach is full strength or no... MarianParoo recommended I do this during my SLAM and it was not until I did that I discovered mine was about 1/2 strength. Once I actually did it things moved much quicker.
 

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