Radiator Bleeder Valve

1/8-Inch Male pipe thread. Easily opened with key, screwdriver, or coin.

If you have a hot-water heat radiator that’s not heating, the cause is usually trapped air, and getting rid of it is simple. At the top of your radiator, there should be a small valve. Use a radiator key, 1/4-in. 12-point socket, or a flat screwdriver (depending on your valve type) and slowly turn the valve counterclockwise until water starts dripping out. This will release trapped air and let hot water into the cold fins. While you’re at it, you should repeat the process with your other radiators. Bleeding the radiators will lower the pressure in your system, so you might have to slowly add water to increase the pressure. Do this by opening, then closing, the valve on the water pipe above the boiler. In fact, you may need to add water while bleeding the radiator in order to purge the air from the system. How much pressure you need depends on how high the water has to rise. The basic rule is 1 lb. of pressure for every 2 ft. of rise. Your gauge may read in pounds, feet or both. A basic two-story house, with the boiler and expansion tank in the basement, needs 12 to 15 lbs., or 25 to 30 ft., of pressure.