I generally learn more by reading forums than by posting, but thought it was time to report in.
As previously mentioned on this forum, I had drained 2/3 or more water to reduce CYA from 130 to acceptable. My after drain CYA level was 20 or less according to my TF-100 kit. Just for comparison my wife took a sample to the most reliable local pool store and they tested the water at 30. I decided to raise my <20 number to approximately 30-40 using trichlor tablets. We had to go out of town anyway so it was a convenient time.
Pool is now crystal clear and no sign of algae. The latest numbers with the TF-100 are:
FC- 2-4 generally
CYA: about 30
Now here is where I would like some input. My wife and I are both wondering about the true level of CYA. It seems to both of us that we can nearly always see the black dot in the tube. Again out of curiosity we took a sample to the above mentioned pool store and were measured at 45 ppm CYA. They are consistently measuring us 10-15 ppm higher than our TF-100 kit seems to indicate. I know both numbers are acceptable, but I would like to know how accurate I can expect to be so that I know when I have flexibility to use trichlor tabs while we are out of town. I have found (as most folks here have) that a little trichlor goes a long way.
Thanks in advance for your answers.