How to Bleed House Radiators

House radiators work by channeling hot water through them and releasing that heat into the rooms in which they are placed.They are generally made of cast iron and were a popular way to heat houses throughout most of the first half of the 20th century. One of the main problems with house radiators is that air sometimes becomes trapped inside them. When that happens, a bubble of air impedes the flow of hot water and stops the hot water from circulating. The only way to remove that air bubble is to bleed the radiator and restore the water flow inside.


Turn off the power to your water-heating system by turning off the power at the breaker. Alternatively, turn the thermostat on the radiator all the way down.


Locate the bleeder valve on the radiator. The bleeder valve is usually near the top, on the side that contains the water-outlet pipe. It may look like a small pipe nipple protruding from the side.


Insert the correct device that will turn the valve on or off. For example, this may be a specifically made bleeder key that came with the radiator, it may be a screwdriver that is inserted into the bleeder valve or you may use a ratchet and a small hex-head socket that will turn and open the valve.


Place a cup or bucket beneath the valve. Slowly open the valve. If there is air trapped inside, it will hiss and sputter as it vents out of the valve. When water begins to run clean and clear into the cup or bucket with no air bubbles present, the radiator has been successfully bled. Close the valve. Turn on the breaker or turn up the radiator's thermostat.