Thanks for the replies--

To answer the questions, municipal water source, and I don't know about calcium. Can't even remember if theres a test for that in the great blue bucket.

No heater either.

I've tried scrubbing with a plastic scrub brush, and green scrub pads with no noticeable difference.

I'll suffer through the controlled drainings to knock down the CYA. Seems like when I drain over the winter, it would help that out, but I guess not enough!!