Bleed Air from Hydronic Heating System Baseboards
Why it matters
Air pockets in baseboards create cold zones (uneven heating) and reduce efficiency by 10–20%. Bleeding air is a simple 30-minute task that saves energy and improves comfort.
Stop forgetting to do this.
Hearth generates a personalized maintenance schedule so you never miss another bleed air from hydronic heating system baseboards.
How to do it
- 1
Turn on the boiler and run the system for 15 minutes to circulate water and release trapped air.
- 2
Working from the coldest room first, locate the small bleed screw (nipple) on the end or side of each baseboard, usually 3/4 inch from the top.
- 3
Place a cup or cloth under the screw to catch water spray.
- 4
Turn the screw counterclockwise 1/2 turn; listen for a hissing sound (air) and watch for water spray.
- 5
Once a steady water stream appears (no more hissing), turn the screw clockwise to close; repeat for each baseboard in the home.
- 6
Return the boiler to normal operation and feel baseboards for even heat; retest in 30 days if cold spots persist.