During the normal heating cycle, the air in your hydronic heating system’s water is forced out.
This air builds up in the water lines, and you may start to notice some unusual discrepancies in your heating system over time.
Air build-up effects in your water lines may range from noisy operations, uneven heating, to total water circulation blockage. When this happens, you have to bleed your hydronic heating system to eliminate the trapped air. Bleeding is a maintenance practice usually carried out once or twice a year. You do not require an HVAC repairman’s help for this routine. Begin by turning off your heating system at the thermostat. 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 typically about an inch tall, with a small nozzle on one side and a slotted screw head on top. Also, check behind the end cover or a radiator shroud as this HVAC equipment point may conceal them. Place a container under the bleed valve to catch water sputters that will come out through the valve. 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. Do not close the valve until you achieve a steady stream of water flowing out of the valve. If no water pours out of the open bleed valve, you’re probably dealing with a corroded bleed valve or a closed supply valve line. Call an HVAC technician to fix this problem. After successfully bleeding your heating system, turn your screw clockwise to close the bleed valve and remove the container. Repeat the bleeding process on the next bleed valve. If you have several bleed valves along the line, then replace the shroud or cover.