Our church building is a one story brick structure (no Basement) that covers 3,000 square feet and is heated with a single hot water low pressure boiler (12-20lb water pressure/weil mclein). The system is a two (2) zone system driven by two (2) circulating pumps. There are two bathrooms, a fellowship hall, nursery, office, Sunday school room, narthex and sanctuary. Surface mounted convector units (6) and wall mounted convector units are used throughout the building. The sanctuary is where we are experiencing our trouble. We have recently been plagued with air in the feed line. We had a licensed plumber check out the system and install an air vent at the highest point in the supply line by the sanctuary. Today we bled the line again in order to get water flowing. We are perplexed as to what may be causing us to have to keep bleeding this supply line every few days. Any advice or suggestions would be most helpful. Bill McNicol, Grace of God Lutheran Church, 1000 Demorest Road, Columbus, Ohio.

Either air has not been removed all the way from the system OR more air is being introduced into the system it is that simple. Without being there to check it out it could be caused by almost anything that would allow air into the system. Most of the time if water is being added to the system by auto feed or manually the air is mixed in with the feed water and when heated the air is released causing the problem. Once the air is removed it is OK unless more water is being added all the time as if there is a leak in the system.