Bleed Radiators and Check Boiler Pressure

If you heat with a hot-water boiler and radiators: air trapped in the system collects at the tops of radiators, preventing them from heating fully and creating banging or gurgling sounds. Turn your heating system on and let it run 15 minutes. Starting on the top floor, locate the bleed valve on each radiator (a small square or slotted fitting at the top of the end cap). Hold a cloth or small cup under the valve. Use a radiator bleed key or flathead screwdriver to turn the valve a quarter-turn counterclockwise. Air will hiss out — hold the valve open until water flows steadily (no more air), then close it firmly. Work down floor by floor. After bleeding all radiators, check the boiler's pressure gauge — it should read 12–15 PSI when cold, 18–22 PSI when hot. If pressure is low, use the filling loop to add water. If pressure climbs above 30 PSI, have the expansion tank inspected. This annual task is the most cost-effective way to maintain radiant heating efficiency.