How to Flush Radiators At Home

How to Flush Radiators At Home

how to flush radiators

Knowing how to flush radiators can drastically improve the efficiency of a central heating system. There are several big giveaways that your radiators require flushing. Are your radiator panels cold to the touch in places? Are you having to bleed them more regularly than usual? Perhaps your boiler is making unusual noises and working harder to heat your home at desired temperatures. All of these are signs that it’s time to flush your radiators.

When radiators aren’t flushed, sludge is allowed to form inside, causing circulation issues that can impair performance. This sludge is a build-up of limescale, rust and grime. Eventually, this sludge can lead to significant blockages. If your central heating system has enough blockages, your boiler is going to have to work twice as hard to heat your home. Sludge can also lead to a boiler breakdown. The good news is that flushing radiators are easier than you might think.  

How To Flush Radiators: What You’ll Need 

If you’re attempting to flush radiators yourself, you’ll need to gather a few basic items before you begin. These include: 

  • Old dust sheets or towels
  • Large bucket  
  • Radiator key  
  • Spanner 
  • Hose pipe

Getting Started

Before you start thinking about flushing radiators, you’ll need to ensure your heating system is turned off. This isn’t as simple as switching off your boiler and thermostat and getting to work. Once your heating has been turned off, make sure your radiators have been allowed to cool down completely. Depending on how long you’re heating has been on, this can take up to half an hour. 

Next, make sure the flooring around your radiators is protected. Reach for those old towels or dust sheets to protect delicate floors from any dirty water that escapes. Now you’ve done this, we can start talking about how to flush radiators. 

It’s vital that you turn off your radiator valves. On one side you’ll find a thermostatic radiator valve. These can be rotated by hand. Make sure you turn this valve all the way down to zero. On the other side of your radiator, you’ll find a lockshield valve. First, lift the plastic valve cap away. You can now use a spanner to turn the valve in a clockwise direction.  

Bleeding Your Radiators

how to power flush radiators

Keep hold of your spanner as you’ll need it to loosen the thermostatic radiator valve. Once you’ve loosened the valve nuts, you can use your radiator key to release the bleed valve. This will allow any excess air pressure to escape from the radiator. 

Make sure you’ve placed a shallow bowl or bucket beneath the valve to collect any dirty water or sludge. Repeat these steps with the lockshield valve on the other side of your radiator panel. Once your radiator has been drained completely, you can close the valves again with the radiator key.  

Removing Radiators from the Wall 

Now you’ve drained and bled your radiator, you can remove it from the wall. Although the previous steps should have removed a lot of sludge from your radiator, you’ll want to take it outside to flush it. To prevent any debris from escaping and ruining your floors, think about wrapping your radiator while you move it.  

Flushing a Radiator 

Flushing a radiator is fairly straightforward. Now your radiator panel is safely outside, attach your hose pipe to the valve inlet and turn on the tap. To ensure as much sludge as possible is removed, make sure you’ve got the tap turned up all the way. 

Sometimes, even high-pressure flushing with a hose won’t get rid of every bit of sludge. Think about using a rubber mallet to give any stubborn sludge a helping hand. You’ll probably need to repeat this step several times until the water runs clear from the other valve.  


Once you’ve finished flushing your radiator, you can reconnect it. Be careful when repositioning it back in place and ensure you’ve secured all nuts tightly. You’ll need to remember to open the valves on either end of your radiator. Finally, use your radiator key to remove any trapped air.  

Final Checks

pressure valve on boiler

When flushing a radiator, you’ll almost certainly experience a drop in boiler pressure. Thankfully, this is relatively simple to resolve. If your central heating system is turned off, your boiler pressure should be no higher than 1.5 bars. If the pressure levels are reading below 1, your system needs repressuring. To repressurise your boiler, simply use the external filling loop.  

Still Having Trouble? 

Understanding how to flush radiators can make your heating system more efficient. However, you’ll need to take pre-emptive steps to stop radiator sludge from returning. Chemical treatments can help stop particles from forming and clogging up your system. 

If you’re considering a gas boiler replacement, it’s also worth thinking about installing magnetic filters. These filters prevent metallic particles like rust from finding their way into your system. 

Ultimately, the best way to combat radiator sludge and an inefficient heating system is to invest in an annual gas boiler service. If DIY flushing hasn’t resolved the issue, it’s also worth investing in a plumber that can effectively and professionally help with power flushing your radiators. 

Looking for a Professional To Do It Instead? 

Have you tried flushing radiators but still have problems with your central heating? It’s time to call in the experts. At Complete Plumbing Solutions, our expert team is ready and waiting to help with all your power flushing needs.

Our expert team has experience with a full range of heating systems. No matter what boiler model you have or how complex your heating system is, we’ll have you back on track in no time at all. Ready to talk more or chat about the cost of replacing a boiler? Schedule a call back today or speak to the team directly at (085) 169 4244. 


Can I flush a radiator myself? 

Flushing a radiator yourself is easy if you are good at DIY work. However, you might struggle to notice any significant improvements to your heating system if sludge build-up is particularly pronounced. If it’s been many years since your radiators were last flushed, it’s best to call in a professional plumber. 

Should I flush my radiators? 

Yes, flushing radiators is essential if you want your heating system to work as efficiently as possible. How often your radiators will need flushing depends on a few factors, including the age and model of your boiler. Generally speaking, radiators should be flushed once every 5 to 6 years. 

What happens when radiators are flushed? 

During power flushing, clean water is fed into your heating system to remove rust, sludge and other debris. The result is that your system will be using clean water. If you’re calling on the services of a professional, they’ll often use an inhibitor solution to prevent sludge from accumulating in the future.  

How long does it take to power flush radiators? 

Flushing a radiator yourself can take as little as 90 minutes. However, an entire central heating system can take up to 8 hours. It may take slightly longer if your system is particularly large or complex.  

How often should radiators be power flushed? 

Ideally, a typical central heating system should be power flushed once every 5 to 6 years. This will ensure your radiators and central heating system remain in a good condition. However, water hardness and radiator materials may mean you’ll need to invest in it more regularly.