MirGSS, Thank you for your readings. As you can tell from Duraleigh's questions, your levels do raise a few concerns. In addition to what he asked, I would mention the following:
- TA (60) Borderline. I'll come back to that through (below).
- CH (190), is a little low from the Recommend 250-350; but I'll com back to that too (below).
- CYA, ideally you don't want to let it go below 30. You might want to add just a little to get your through the winter.
- Chlorine (FC): Even though you are about to close (which is why I assume your pump is off), it should never be zero. So if your pump is still connected and operational, I would definitely add some bleach right away to get you to about 4 ppm.
- pH (?) This is important to know right now and I'll tell you why. It's related to your low CH and current TA. Because you have a plaster pool, you have to ensure CH and/or the CSI (Saturation Index) are within acceptable ranges. Too high = scale; too low = damages plaster. You can see your "CSI" level on the Poolmath calculator. If I enter your current CH (190) and TA (60), and I "assume" your pH is 7.5, then your CSI is acceptable. But if your pH goes below 7.4, then your CSI reading exceeds the -.6 range, and you could experience damage to plaster.
If your pump is still connected and you can mix the water, I would recommend the following:
1. Add bleach ASAP for target of 4 ppm. When you close, you go to shock level of about 12 ppm.
2. Add baking soda to bring TA up by 20 ppm (new target of 80 ppm); this helps make-up for the low CH
3. Ensure pH is at/about 7.6 (This also helps your CSI level to make-up for the low CH).
Let it all mix for about an hour and re-check. If those numbers are good, then keep them that way until water temp stays below 60 and prepare to close. Sorry this was a little more lengthy reply than I wanted.
Hope it helps.
