First time SLAMing. Is it going okay?


Well-known member
Nov 27, 2020
Background: 16,700 gallon plaster pool, salt. 3 months old. I have the SWG-40 salt cell rated for 40,000 gallons. Since we added salt 2 months ago, the SWG has been set to 100%, pump running 12 hours a day at 2100 rpm. Chlorine levels never get above 2 to 2.5. Water always looks clear. But I can't explain the high chlorine consumption. Last week I lowered the SWG to 80% just to see if it could keep up with it. But yesterday morning, the deep end looked cloudy with some greenish something along one edge. By the afternoon, the whole deep end looked very green.

Based on guidance here, I decided to SLAM yesterday afternoon. I also have the TF-100 kit. Reading before the SLAM:

FC: 2
CC: .5
pH: 7.4
CH: 450
TA: 70
CA: 50
Salt: 4000
Temp: ~88f

I used pool math to get FC up to 20ppm. Within hours, the pool looked clear again. Also, FC dropped to 13. I added 2 more gallons bleach after dusk to get back to 20ppm. This morning, the pool looks about as good as it ever did. (See pictures, although the green areas didn't come through very well). I still see some slight green in some areas the vacuum doesn't really get. (Brushing didn't seem to help much either). Surprisingly, FC is testing at 15. (I also left the filter on with the SWG running at 100% overnight). Pool math says I need another gallon.

Seems like I lost 5ppm plus maybe 2ppm from the SWG for a total of 7ppm overnight? Is this a normal amount of chlorine drop? It seems high to me. Of course, it's only been about 18 hours. I assume I keep going at this rate? Eventually I have to stop losing so much chlorine right? It's more than the SWG can even keep up with.


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