This winter I noticed a faint noise from the baseboard heat in our house (gas-fired boiler with two zones- one for upstairs and one for downstairs). I suspected air in the lines so I bled them out. I’ve done this quite a bit since we moved in because we’ve rearranged the locations of the baseboards to facilitate a kitchen remodel. Sure enough, there was air in the pipes. After bleeding the pipes, the faint noise was gone but now when the heat kicks on, I hear water gurgling through the pipes. Again, I figure there’s still air in the system so I bleed it again but it doesn’t seem to improve the situation. The gugrling goes away about 10 minutes after the heat comes on but the initial noise is pretty anoying.
I’ve repeated this procedure probably a dozen times over the last week to no avail. I’ve not noticed any leaks in the system either. Everytime I open the spigots to bleed the system, there’s a lot of air. I guess my question is this: is there something basic I should be checking on the system that may be malfunctioning and allowing air into the pipes? Since we’ve lived in this house, I’ve completely drained the system and refilled it several times and have never had this much trouble with air in the lines. The system is set up with an automatic fill valve from the city water supply if that makes any difference. I’d appreciate any suggestions. Thanks.