How to Bleed a Hot-Water Radiator

Have you ever noticed one of your hot-water radiators isn’t coming hot even though the heating system’s working and all the other radiators in the house are operating as normal? Or maybe that a radiator is hot at one end but stone-cold at the other?

If it’s a hot-water radiator it’s probably nothing more serious than an air bubble preventing the water from flowing.

This is an easy fix. All you need is a radiator key (or possibly a flat-head srewdriver), some rags, and perhaps a small pan to catch any water.

simply-green-biofuels-radiator-bleed-1At one end of the radiator, at floor level, you’ll see a valve. This is the intake valve through which water enters the radiator. At the opposite end, again at floor level is the exit valve. At the top of the radiator, at the opposite end from the intake valve, you will see a much smaller valve, typically a square fitting set into the radiator itself. This is the bleed valve.

simply-green-biofuels-radiator-keyFirst make sure the intake valve is open. Then use your radiator key to slowly open the bleed valve. (A radiator key is an inexpensive item that can be bought at any hardware store but if you don’t have one some valves may be opened with a small wrench or needle-nose pliers. Some modern radiators have bleed valves designed to be opened by a flathead screwdriver – check before you head out to the store.)

As you open the valve, you will hear air escaping. Hold a rag or small pan beneath the valve. When all the air has been released, water will start to come out. The flow will sputter at first, but eventually will come smoothly, even fast. Once you have a smooth flow, close the bleed valve, wipe any water off the radiator, and make sure there are no leaks.

Move on to the next radiator – if you’re bleeding one radiator you may as well bleed them all so you know there’s no air trapped in the system.

And that’s it! No fuss, no mess, just uniformly warm radiators heating the room as they were designed to do.