How to Bleed a Baseboard Hot Water System

Radiators get heat from water heated in the boiler.

Many older homes use a baseboard hot water system to provide heat. In this system, water is heated in the boiler and sent throughout the home in pipes located at the base of the walls or in radiators. When the water cools, it goes back into the boiler and is reheated to start the process again. Occasionally, air seeps into the hot water lines, which can cause bubbling or gurgling noises and prevent water from completely flowing through the system. Fix this problem by bleeding the system.

Things You'll Need

• Garden hose
• Bucket

Instructions

1. Turn the boiler off and record the water pressure in the tank.

2. Make sure the self-feeding water valve is connected to the boiler.

3. Open all of the valves that lead to the different heating zones in your home. Close all of the shutoff valves.

4. Attach a garden hose to a spigot on the return line. This is the line that takes cold water back to the boiler to be reheated.

5. Open the spigot and self-feeding valve to drain the water from the line. Drain the water into a bucket or drain; be careful as the water is extremely hot. Drain the water until you no longer see air bubbles. Monitor the water pressure; if it rises above 25 psi (pounds per square inch), release the self-feeding valve until it drops below 25 psi.

6. Release the self-feeding valve and close the spigot to which you attached the hose. Allow the water pressure to return to its normal level. Repeat this process until every heating zone has been bled.

7. Close all of the zone valves, and open all of the shutoff valves after all zones have been bled.

8. Check the water pressure. Once it hits the level it was at when you started, turn the boiler back on.

References

• diydata.com: Air in Central Heating Systems
• Home-Wizard: Baseboard Heating Systems