Can You Bleed a Radiator When the Heating is On?
The short answer is - you shouldn't! Bleeding your radiator to release trapped air is a regular home maintenance task - and it's highly advisable you turn off the heating. If you don't bleed your radiators periodically, you'll often find that you get cold patches, or the radiator might not heat up at all.
Even if the radiator feels ice cold to the touch, when you release that trapped air, the pressure can be intense and there is a very real risk of suffering a nasty burn.
Here we'll run through some of the signs that it's time to bleed your radiators - and tips to ensure you stay safe.
Signs That You Need to Bleed Your Radiators
Problems with your central heating inevitably occur on the coldest days, so it's important to stay on top of trapped air to ensure your radiators are working well when you need them most!
There are several signs to keep an eye out for, which indicate that there are probably air bubbles preventing your radiators from working properly:
- Cold radiators at the top: if your radiators are warm at the bottom but cold at the top, you likely have air collected at the top, which means the hot water can't circulate properly.
- Completely cold radiators: although less common, trapped air in the pipework can prevent the radiator from heating at all, and it's essential to get the problem fixed before you end up with a burst pipe!
- Dampness and mould: radiators that aren't functioning well are usually a sign that there's an issue somewhere in your piping. Symptoms include mould patches on the walls or dampness without any obvious cause.
- Rattly radiators: older properties typically have a noisy central heating system, but if you're hearing strange sounds such as rattling and gurgling, it's most likely air causing the hot water to bubble up inside the radiator.
Some of these scenarios might suggest a bigger issue, but the best place to start is by bleeding your radiators - you'll either solve the problem or clarify that air bubbles aren't the cause.
What Equipment Do You Need to Bleed a Radiator?
You don't need a professional plumber to bleed a radiator (although you can certainly call one if you're not confident or able to carry out the task yourself!).
The equipment you'll need includes:
- A radiator key.
- Something to collect excess water with, like a bucket or jug.
- A cloth to clean up any spills and protect the floor.
As we've mentioned, it's worth turning off the heating before you bleed a radiator, as the hot water in a central heating system can get extremely warm.
However, it's also advisable to wear a pair of safety gloves, especially if you haven't waited for the radiators and pipework to cool down completely.
How to Bleed a Radiator Safely - Step By Step
The first job before you bleed a radiator is to turn the heating on. That's so you can double-check which radiators are working and which aren't.
You can inspect each radiator, ensure that the heat is even across the surface, and identify which radiators have cold patches or intermittent warmth.
We'd recommend you wear your gloves for this step since there is always a burn risk when touching heated surfaces.
When you've spotted the problem, you'll need to:
- Turn the heating off: radiators can get very hot indeed, and sprays of water can scald the skin, so it's important to let the system cool to avoid any risks.
Prepare for water drips: depending on how long it's been since you last bled your radiators, you might get a fair amount of water. Placing an old towel under the bleed valve (the round hole at the top with the square in the middle) will preserve your floors. - Open the radiator valve: insert your radiator key into the valve, which releases the trapped air. You'll need your bucket or jug to catch any water and will hear a hissing noise as the air escapes.
Close the valve: when the hissing has stopped, water usually starts to leak, so you need to turn the key clockwise to close the valve safely. - Check on your boiler: finally, check on the water pressure in your boiler. Pressure below one bar usually means the system needs re-pressurising, whereas pressure between one and two bars means you're fine to turn the heating back on.
Tip - lots of radiators end up being painted at some point, so it's not unusual for the radiator valve to be stiff.
To unblock a valve, you should close off the inlet and outlet valves at either end of the radiator and then take out the screw in the middle of the valve - turning your radiator key anticlockwise will then release the trapped air.
Frequently Asked Questions - Bleeding a Radiator With the Heating On
Here we'll answer some of the frequently asked questions about bleeding radiators at home - including the importance of turning off the heating!
Why Can't I Bleed a Radiator Without Turning Off the Heating?
Radiators run from your central heating system, so they are full of extremely hot water.
Even cold radiators with trapped air can release spurts of scalding water when bled, so it's advisable to turn the heating off completely until you've finished bleeding your radiators.
How Regularly Should I Bleed My Radiators at Home?
It's worth checking your radiators every other month, and certainly in the run-up to winter when you want to ensure your heating is in good condition before the colder weather arrives.
Bleeding your radiators every two months is a good way to avoid any potential damage to pipework, caused by a build-up of trapped air in the heating system.
How Can I Check if I Have Bled My Radiators Properly?
The hissing noise indicates that you've successfully released the trapped air in your radiators.
When you turn the heating back on, you should feel the radiator warming up in a few minutes and can check the water pressure in your boiler to ensure it's all running correctly.
References:
- https://www.shellenergy.co.uk/blog/post/how-to-bleed-your-radiators
- https://www.eonenergy.com/boilers/heating-hub/issues/how-to-bleed-a-radiator.html
- https://www.viessmann.co.uk/heating-advice/how-to-bleed-a-radiator
- https://www.homeserve.com/uk/living/heating-and-cooling/how-to-bleed-a-radiator/
By Johnny Fuller
Home Improvement editor at NWrenovations.com
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