I have been doing the TFP method for ~18 months with good results.
I have 15k in ground plaster. My CYA has been ~100 and reducing since beginning TFP. I have been maintaining 10 ppm chlorine and needed to shock twice to 30 ppm in the past year when I neglected to monitor chlorine.
I use k-2006 to test, but take a sample to my pool store to let them check my CYA. Eveytime they tell me that my chlorine is way too high and unsafe for swimming and unsafe for my equipment, but they insist that 100ppm CYA is appropriate. I hate to think that I understand pool chemistry better than my pool store owner after reading TFP method and forums for a few hours, but their recommendations are contradictory to my understanding of chemical interactions. This past time they even told me that it would be illegal to tell me that my pool was safe.
Am I missing something?
Does the chlorine sanitization effectiveness as related to CYA level also relate to corrosive effects on equipment?