During the normal heating cycle, the air in your hydronic furnace’s water is forced out… This air builds up in the water lines, and you may start to notice some unfamiliar discrepancies in your furnace over time, but air build-up effects in your water lines may range from noisy operations, uneven heating, to total water circulation blockage…
When this inevitably happens, you have to bleed your hydronic furnace to eliminate the trapped air. Then bleeding is a service practice usually carried out once or twice a year, however you do not require any heating and A/C repairman’s help for this routine. Begin by turning off your furnace at the thermostat, then find the bleed valve located on the radiator, furthest from the boiler. These valves are small, cylinder-like fittings that stick up from the supply pipe. They are officially about an inch tall, with a small nozzle on one side and a slotted screw head on top as well. Also, check behind the end cover or a radiator shroud as this heating and A/C machine point may conceal them, place a basket under the bleed valve to catch water sputters that will come out through the valve, but slowly open the bleed valve by turning your screw counterclockwise. There should be water sputtering out accompanied by air hissing out through the bleed valve’s nozzle, however do not close the valve until you achieve a steady stream of water flowing out of the valve, then if no water pours out of the open bleed valve, you’re truly dealing with a corroded bleed valve or a closed supply valve line. However, call an actual heating and A/C serviceman to service this problem. After successfully bleeding your furnace, turn your screw clockwise to close the bleed valve and remove the container! Repeat the bleeding process on the very next bleed valve. If you have several bleed valves along the line, then replace the shroud or cover as well.