High CYA SLAM

[NickinLA]

Greetings, I'm hoping to get some input into my SLAM process to ensure I should continue with it.


My pool was built in December and the levels have been great. About a month ago, I started to lose FC at a rapid rate, with FC often coming down toward 1 or zero. I have a 6-month old SWG cell with all of the light indicators looking good and the salt level fine (3,200 per a manual test; the SWG doesn't look like it needs to be cleaned at all). The pool has an Aquabright finish and the water has been clear. After a month or so of needing to add liquid chlorine, I decided to try a SLAM to see if that would help.


I started the SLAM this past Friday, about 72 hours ago. Tried to brush it once a day. My CC was 1.5 after starting the SLAM, and is now down to <0.5. I'm still losing FC on the overnight test though... Here is where I'm at:


FC 27.5 (this AM; was 31.0 last night...)
pH 7.6 (3 days ago, just before SLAM)
TA: 110 (18 days ago)
CH: 120 (18 days ago)
CYA: 90 (I probably should have drained out some of the water so I would be lower in CYA when starting the SLAM...)


I'm wondering if 72 hours is long for a SLAM on clear water, or if I'm just getting started and should plan to continue at the SLAM level (35) until the overnight test actually shows <1.0 FC loss. Also, any chance my high CYA would contribute toward the overnight loss, or is that only bad because it affects the amount of chlorine needed for the SLAM?


Any advice would be tremendously appreciated! Thanks

 

[mknauss]

Attempting to do a Overnight Chlorine Loss Test at very high FC levels is problematic. The error in your drop size and overall testing regimen is easily more than 1 ppm at 30+ ppm FC.

If your water is clear, really clear, and your CC has been at 0.5 or less at your first test in the early AM, then I would suggest letting your FC drop to the range of 15 ppm or so and then run a Overnight Chlorine Loss Test. You may find you pass it.

As the FC drops, keep an eye on the water clarity, and test the FC and CC in the early AM. If you show greater than 0.5 CC at that test, restart your SLAM Process and run it another few days.

Hope that helps

Take care.

 

[NickinLA]

Fantastic. I really appreciate that advice and will give it a shot!