Hi You All,
I tested today (Mon.) and got these latest results:
pH 7.5 (maybe 7.6)
Prior to this, my CYA was at 50, as I had completed a partial drain/fill in mid June to bring it down from 100+. Additionally, the CH was very high in the 1000s, and after the parital drain/fill it was at about 700 or so. And, I lowered the TA from 180 to 80. Water temp is perhaps 85 degrees. I use a TF100 kit. FWIW, right now the chlorine stash I am using is 12.5%. When I finish the last 2.5 gal., I will hit my stash of 10% chlorine (Kem-Tek brand from OSH).
Couple of questions:
1. How can the CYA drop like this? Is it affected by the normal water replacement due to evaporation? It seems that every 1-2 weeks or so I am topping off the pool. When I tested the CYA today, I dumped the sample back in the mixing bottle so that I could try it again to see if I was accurate. After 4 times, I kept getting roughly the same results maybe varying by 2-5. But, per the instructions with the TF100, it says to use the number you are closest to, which for me would be 40. On a different note, could the CYA drop from the addition of MA?
2. Should I bother raising the CYA back to 50, or just keep it at 40? Any problems with a CYA of 40? I had read some posts that having a lower CYA may lead to the possibility of greater chlorine burn-off. Would I really see that, or any difference in a level of 40 vs. 50, besides having different goal and shock amounts?
3. I was going to add 49 oz of 14.5% MA, per Pool Math based on my results, to lower the pH from 7.5 - 7.2. I generally see my pH rise over a week up to around 7.5+. In order to have a balanced CSI, I bring down the pH to 7.2 and let it rise again over the subsequent week to 7.5 or so. The problem is that today, out of curiosity, I plugged in 49 oz MA in the "Effects of Adding Chemicals" section to see if it would have any effect on my lower TA of 70. As there was not an option for 14.5% MA, I chose the closet which was 15.7% MA. Low & behold, it showed that 49 oz of MA would lower my ph by 0.31 and lower my TA by 5. I did not add the MA yet, b/c I wanted some input from here. Do you normally add baking soda to counter the expected drop in TA by the MA addition? FYI, I have been adding MA approx. weekly to keep my pH in line and in my tight parameter of 7.2-7.5. Guess perhaps this may have been the culprit that lowered my TA from 80.
Tx for any help you can shed here.