Bathroom Remodel - Cast Iron to Baseboard

S. Diemer

I recently had a small 2nd floor bath remodeled. As part of that job the plumber replaced the cast iron radiator with a 3 ft baseboard. (The house was built in 1928 and converted from a gravity system to circulating system in 1990.)

When the remodel was done, no hot water flowed from the boiler to the bathroom. There are 2 other rooms that are serviced by this flow main (1st floor Kitchen toekick heater and 2nd flr. bedroom cast iron radiator)both of which are later in the line and continued to get heat.
The assumption was the water took the path of least resistance and bypassed the smaller cooper tuning in the remodeled bath.

To work around this the plumber then diverted all the water from the flow main up into the remodeled bath and fed the return from the bath back into the flow main in the basement which leads to the other 2 rooms. Now the bath has heat but not the kitchen or the 2nd flr bedroom. There is a circulating pump that assists the flow to these last 2 rooms on the line but that doesn't seem to help. The heat makes it to the pump but fades before it gets to the next 2 rooms.

At this point I'm thinking we should have left the Cast Iron radiator in the bath. (Too Late Now). Was the plumping alternative described above realistic?? Even if we can get the hot water 'flowing' through this loop, I'm concerned about the distance the water needs to travel and the fact that 3 rooms of heat need to flow through a 3' baseboard heater. Won't it cool off too much to really heat the other 2 rooms? (Help)

I'd appreciate thoughts on what to try next.