How To Bleed A Radiator

A radiator’s efficiency can begin to degrade when air or gas gets trapped and prevents the hot water from properly heating the radiator. Bleeding off the air pressure can get your radiator working again. This is a relatively simple operation, but be sure to follow all the steps carefully.

Before you begin, open all the thermostatic radiator valves and turn up the heat in your home or office so all the radiators come on. Run the central heating for about ten minutes, and then turn it off. After that, check each radiator individually to see if they’re heating up. Be careful not to burn yourself — radiators can get very hot.

A cool spot somewhere on the radiator can mean that trapped gas is preventing it from operating at full efficiency. This can be resolved by bleeding the radiator. Gas is most often trapped at the highest point in the building or environment.

Bleeding the Radiator
Important: Before you begin, make sure your central heating is fully switched off — not only for your own safety, but to make sure no more air gets trapped inside the system while you’re working.

To get into the radiator, you may need a specialized radiator key. Many newer radiators can be opened with a simple flat screwdriver. A radiator key is generally available at any hardware store.

The next step is to release air from the radiator. Insert the key (or screwdriver) into the bleed valve (or bleed screw) at the top corner of the radiator and turn counterclockwise.

As the air escapes you will hear a hissing noise, if there is any in there to begin with. Once water begins to drip from the open valve it means all the air has been successfully bled from the radiator. Turn the key clockwise again to close and tighten the bleed valve.

You will want something absorbent on hand to deal with drips. A simple cloth or tea towel should do the trick. Be advised that the water leaking from the radiator is likely to be very hot, so use caution.

Follow-Up Steps
Repeat this process for each of the radiators in the home or office. Once you’re finished, turn the central heat back on and check to make sure that everything’s working properly and none of the valves are leaking.

Bleeding the radiators will lower the overall pressure in your central heating system, so you may have to top-up the boiler afterward. Usually, this involves slowly opening and closing the main water valve above the boiler. If you don’t feel familiar enough with your central heating system to do this, get a professional plumber to do it.

When checking the radiators, be sure to look for any cold spots or uneven heating. This can be a sign of more serious problems, like rust or sludge built up in the bottom of the radiator. That’s not a problem you can fix yourself — have the radiator flushed.

Also, if some of your radiators are cooler than others that means that the radiators nearer the central heating system are using more hot water than those further away. That’s also a job for a professional plumber.

Once again, if you don’t feel comfortable doing this yourself, don’t! It also can’t hurt to check your home insurance before doing any sort of DIY work — bleeding a radiator is a fairly simple operation, but it’s always better to be safe than sorry. Staunch & Flow are a professional London plumbing service and would be happy to help with any questions you may have.