The heat quit working on the top floor of 345 Blaine. There were 2 issues that
caused the problem.
The automatic intake valve was clogged (Bill said they need to be replaced every 8
years or so). The purpose of the automatic intake valve is to allow new water
into the system. I believe only about a pint of water is lost and refilled
There were a few leaks at the zone valves (Bill said the leaks were due to gasket damage caused by antifreeze).
So the system was losing water and was unable to refill itself. That
caused a lack of pressure (it was about 5 psi instead of 12 psi) which
prevented hot water from reaching the top floor.
Bill fixed the problem by replacing many components: automatic intake
valve, backflow preventer, electric pump, and all zone valves. He also
removed the antifreeze, refilled the system, and bled the air.