Thank you. I should mention that I've been away from the house so much that I haven't been able to start the SLAM, but I think I'm ready to start, but have another question. I just checked my CYA level, and it's unusually low: 27. I thought last season, it was up around 70. (By the way, I have a SWG, but I haven't turned it on yet this season, as I want to SLAM first before doing that.)
Does it makes sense that it could get that low? I thought you really had to drain the pool to lower it that much. I will say, I recently got finished repairing a stubborn leak in the pool jet inlet adapter (I have another thread here about that), I had to drain the water to the bottom of the hole that's behind the jet to work in it, so I guess that could explain part of the drop, but still, 27 is a big drop.
Could the presence of algae be affecting my measurement? I read a tip here in another thread to use a coffee filter on the water before doing a CYA test, and that's what I did.
Anyway, I guess with a measurement of 27, I should raise the CYA before starting the SLAM. I do have on hand over a dozen 3 inch chlorine tablets, which I know will raise the CYA level, plus as a bonus, the free chlorine it releases into the water should help kill the algae as well, so I guess I'll do that. I need to find out how much each tablet will raise the CYA by, but I know I have an old thread here somewhere that answers that question, so I'll go find that thread.
I remember reading that the danger of SLAMing with not enough CYA is that the chlorine breaks down too quickly, causing the water not to retain enough free chlorine during the times between my checkups. (I like to check each morning and evening on the chlorine levels during SLAMing.) But the Chlorine tablets continually release chlorine, taking care of that problem.
My idea is to maybe put one tablet in a day during the SLAM, and using the charts on this site, projecting what the CYA each day will be during the process, adjusting the free chlorine levels a bit higher each day to compensate for the ever increasing CYA, and at the beginning, while the CYA is still low, I suspect I shouldn't be worried about the quickly dropping free chlorine levels, because the ever dissolving tablets should compensate for that. By the time my last tablet is gone, the CYA should be high enough that the burn off of free chlorine will no longer be a problem.
Still, I'm a little worried about starting the process right now and trusting my 27 measurement, because if it's wrong, will I be able to confirm that before dumping in my chlorine? I.e. can you reliably remeasure CYA during a SLAM in progress, would shock levels of chlorine interfere with that?