In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
I have a 150000btu one pipe system with two primary mains. I notice that neither main has venting at the end as I see written,but, there are two Vent-rite #75 vents on top of two high risers at the ends of the two return systems. Is this location for main venting fairly standard? Should it be as effective as at the ends of the mains?
Assuming this location of venting is OK I would then like to understand whether I have enough. What concerns me is that I have a few radiator vents that seem to work hard with noticeable hissing (although no water or steam release). I can feel with my finger air rushing out of them at some times. When this is occurring I have checked in the basement to see if noticeable air is escaping the main vents and I do not sense that any is. These main vents were installed when a new boiler was installed early in the winter. Could they be plugged or insufficient in size? Or, are they just not located properly. Just a note, when the old boiler was in place I used to see air releasing from these main vents.