1 Zone Heating Another??

I have a problem that hopefully one of the experts in this forum can help me with. I live in a ranch house that has baseboard heating through a gas boiler which feeds 3 zones (basement, bedrooms, and living/dining room).



I've noticed the past few days that when the thermostat is turned "OFF" in the dining/living room but "ON" in the bedroom, the baseboards are giving off heat in the dining/living room as well as the bedrooms. Ive tested the thermostat "ON/OFF" switch that feeds the dining/living room zone and it seems to function properly (the solenoid on the control box on the boiler opens and closes like it is supposed to). When I turn the thermostat that controls the bedroom zones to "OFF" then ALL of the heat is shut off in the entire house (the basement zone is unaffected by either of the other two zones being turned on or off, and the basement zone functions properly).



I always thought the zones were completely independent of each other and didnt share any of the same pipes? So I'm confused how the dining/living room is being controlled by the bedroom zone?



Any advice/help would be greatly appreciated :)

1 Zone Heating Another??