Our lower zone on the first floor was not heating the kitchen, LR, family room - yet the bathroom, believed to be at the beginning of the run - was very hot. Too hot to touch. Plumber thought it was an air block and try to bleed the air out of the line at the boiler to no avail. There are no bleeders that we could find in the run. The automatic fill valve was replaced the month prior, due to being totally clogged with sediment. and ruined. We are assuming that the sediment is clogging the line as well. Of course there are multiple 90 degree bends from the basement up to the baseboard and back down again. Plumber said sometimes you need to just start cutting/disassembling the line to find the clog. That process will be extremely difficult, as former owners have cupboards in the kitchen built over top of it. And, they weren't built and then installed, but rather built in place.
Any ideas or tools to move the sediment and clear out the copper pipes -3/4". Just to add, we have a spring fed well that is hand dug, lined in a diabase rock, and has been going for over 200 years.