I'm in the process of trying to stabilize/balance the water in our new pool. I've dealt with the first round of metal precipitants from my initial FC generation (SWG system), but in the process let the FC go to zero (I didn't take the time to consider just how fast it would drop as I haven't gotten any CYA into the system yet).
I'm receiving my TF-100 test kit tomorrow, so I'm working off test strips for now. Yesterday after having the pool covered and SWG on boost for about 20 to 22 hours, I had a FC somewhere around 15 to 20 (I guess, darkest color on test strip). Today, with the cover off, in full sun for perhaps 7 hours), zero.
It's been a long time since I was in a chemistry class, but I've figured out the half-life of the chlorine must be around an hour (or less) in full sun (82F today maximum). Tonight I started up the SWG after vacuuming the iron precipitants out. After about 1.5 hours there was about 1 ppm FC. I added 30 ounces of 8.25% bleach to get what I assume, if I used the pool math calculator (and Richard Falk's pool chemistry spreadsheet) correctly, would be around a FC of 5 tomorrow morning (assuming no organics eating it, which I doubt at this point). But tomorrow will be sunny, so if I use 1 hour as the half-life, I will be back to basically 0.15 FC in 5 hours of full sun. The pool is getting around 8 hour of full sun right now. I understand the half-life is dependent upon a bunch of things, but if I assume only UV radiation is breaking it down, is a half-life of one hour correct? I started to read this (http://standards.nsf.org/apps/group_...lorine-CYA.pdf) and decided I'm looking for the cliff notes!
So my questions are this:
- What level of FC should I be maintaining when and after I add the CYA tomorrow evening (shooting for 70 to 80) as I wait for the CYA to full dissolve? Should I drive it up to 15 to 20 every night until the CYA kicks in? Should I drive it to 5 or 6 then cover it?
Tomorrow evening, I'll be putting in around 3 lbs of solid CYA, if I used the pool math tool correctly. Questions on this are:
- How long will it take for the CYA to fully dissolve and take affect? Does it take a week, a few hours, or? I understand it may take up to a week for it to show up in the water test.
- But, does it start working right away?
- The directions on the CYA say to mix it in hot water and slowly add it the suction side (i.e., the strainer). I have seen in the threads I've read to try to educate myself that people put the CYA in a sock or socks, either tied to the pool wall, or in the strainer (my strainer is currently filled with white paper towels as I anticipate more iron precipitation). Does it matter which method I use? I would think pre-dissolved stuff would ramp up to speed faster, but don't know if matters if it does or not.
I believe the overarching idea here is to get the CYA in there, get it into the correct range for my SWG (70 to 80) and then bring the FC down (assuming I can keep the level high to begin with) to the correct level, and then run my SWC system the number hours daily need to maintain the target FC of 5 per the TFP guidance for CYA in that range, which brings up one last question:
The manual for my Intex SWG system states I should be running the SWG system about 4 hours (really 3.5 but the system only work in hour increments) to maintain the FC level. My question is on this is: Is the run time of the SWG independent of the amount of CYA in the pool? I understand that the FC level required for sanitization is a function of the CYA level (higher CYA, higher FC), but do I need to run the system more to get a given FC for a higher given CYA? I believe the answer is "no," but am double-checking everything.
Thanks again - I wish I could be more helpful. I'm feeling more than bit inadequate. If anyone needs help with questions on mid-year corvette or 1st generation Camaro restoration, submarine weapon systems, or mechanical engineering, I may be able to feel like a worthwhile contributor!