I have the TF100 testkit, and have a pool just under 1 year old and have been using this kit and readings for most of that time. Aside from some calcium scaling on my spa spillway I think it's been going fine. I test all of the below once a week (and FC/PH every 2-3 days) and as of last weekend my readings were (Temp 80):
CYA: 30 (halfway between 30 and 20, since it had been clearly 30 for several weeks prior I marked it as 30 this time too)
After I took this reading I added bleach (to get FC to 4) and muriatic acid (to get PH to 7.5), and added bleach/acid mid-week to try to maintain those numbers. I also had to fill some water on Friday as it was below my water line.
Anyway on Saturday this weekend I measured and got the following (Temp 80):
CYA: 0 (I could literally see the dot with the tube completely filled up). The CYA being 0 I thought was a mistake but I tried the test again and got the same results.
So I'm trying to figure out how my CYA could be zero, especially seeing as it's always been between 30-40 for the past year...the weekend before was the first time I saw it where it looked like it *may* be below 30, but it was between 20-30 at least. Now in one week it seems to be essentially ZERO without any major water change or rain. I hadn't seen any major changes in any of my other readings FC/PH and even my TA seemed normal, and CC was still 0.
So I added some solid stabilizer in sock/skimmer to bring it up 20ppm and was going to check again this weekend, but decided to have TexSun do a test on my water and see what they showed my CYA at. Now they made me scared for something else. Here is what they recorded:
CYA 25 (they show it as a little low, but at least not zero - maybe my stabilizer had already started to take affect though?)
Total Chlorine 2.9
Free chlorine 2.8
TA - ZERO! She told me DO NOT Swim in your pool right now and I need to raise this up.
PH - 7.5 (she scratched through this though, because TA was 0 so said you couldn't trust that #)
Borates 47 (I've never added borates! Was just investigating doing that but she's showing 47 already and I've never added???)
So anyways - my questions
1) should I trust ANY of what TexSun's reading says? Is it possible I'm doing my reading wrong (how could they have me ZERO TA when I have me comfortably at 70?) I realize they may not be totally accurate, but now I'm scared that mine may be way off, especially since I've seen scaling when I thought my PH was never abnormally high (occasionally gets high but I drive it down before it stays at that level). Also is it possible I do have borates in my pool or can their machine be that off? (side-note, I'm getting borate test strips this week as I was intending to use borates in next week or 2, so I guess I can answer the question on this one myself in a few days). Is there anything I can do to ensure my TA reading is correct and there's is wrong? I don't want the kids in the pool if it's dangerous for them?
2) I'm assuming the answer for #1 may just be "trust your own tests over the pool companies", but even if that's so - how could have ZERO CYA all of a sudden? And what should I be worried about there (especially if my FC/CC/PH levels remain good?)
3) I put the solid stabilizer in socks in my skimmer, let the pump run for the past 36 hours and have been squeezing them periodically (to get out the white dust). How long do I leave those socks in there? Will the solid eventually completely dissolve or do I dump it out of the socks at some point? Do I need to leave pump running until it's all dissolved?
Some other points - pool water looks fine, not cloudy, not green...looks normal to me. I don't seem to be having to add way more bleach than normal or anything. PH doesn't seem to be swinging wildly, though it does raise every few days causing me to add acid.
Thanks in advance for the help!