Thank you Doc!

I checked today with two different pool shops the level of phosphates and the level of copper. I do not have my own tests for that.

Both shops measured something around 100-200ppm of phosphates, and 2.4ppm of copper. It seems that the last 4 lb of sequestrant (super Sequa-Sol) did not reduce Cu level, but it was just adding phosphates. It could be that heater is adding copper at the moment, because I did not bypass the heater yet. I will fix that over the weekend and report.

As you suggested, lime-softening can be done with Ca(OH)2, but what form should I buy? Which substance can one buy to soften the water? Thanks!

I was very intrigued by the hardness test today at the pool shop. Most of their measurements agree with my own, except hardness test, which they got 108ppm (as opposed to mine 800ppm), and they suggested to add more Hardness control!!! I will recheck the hardness once more tomorrow.