Unfortunately, over time, central heating systems and particularly radiators, are vulnerable to a build-up of hardened, thick sludge, which begins to impact its performance. If left untreated, you could find that your boiler is being forced to work harder to heat your property, causing a significant rise in your energy bills.

There are two main ways of treating sludge in your central heating system. Professional plumbers typically use a power flushing machine, which in effect, its a large vacuum cleaner for your central heating pipework. However, it is possible to remove radiator sludge through DIY methods, helping you to familiarise yourself with your system and ultimately save money.

Having spent many years working on the home’s of hundreds of clients, we regularly share tips with clients on the various repairs they can complete themselves – flushing a radiator being one. So, we have put together a full guide on how to remove radiator sludge in seven easy-to-follow steps.

Remove Radiator Sludge In 7 Steps

A build-up of sludge is typically only an issue in older radiators as it is made from a mix of dirt and rust. Over time, this accumulates at the bottom of your radiator, which in return, prevents hot water from being able to flow effortlessly through the system. This creates cold patches on your radiator, often leaving homeowners turning their central heating up a few more degrees to accommodate for the lost heat.

Through our many years of visiting clients for their annual boiler service in Towcester and the surrounding areas, we have seen numerous boilers with problems down to untreated radiator sludge. Why? Because the added pressure that you are putting on your system can damage the heat pump, valves and boiler itself. For this reason, it is vital to familiarise yourself with how to spot and rectify this issue. To help, our guide will run through the following:

Hat and Gloves on Radiator

How To Tell If You Have Sludge In Radiator

There are many different ways to tell if you have sludge in radiator, and you will not need the assistance of a professional plumber. The easiest method is to turn your central heating on to full power and open up any TRV’s you have on your radiators. The TRV’s are the small valves on each end of the radiator with numbers imprinted onto them. Allow the radiators to heat up, and being very careful not to burn yourself, gently feel the bottom of the radiator. If any bottom areas of the radiator remain cold ten minutes after turning the heating system on, then the chances of sludge are high. However, if you notice that the bottom of the radiator is ok, but the top is staying cold, you might have air in the system. You’ll need to use a bleed key to release the unwanted pressure. Just remember to check the system’s pressure after bleeding and top it up where required.

If you do bleed your radiator and notice that there is a brown liquid that seeps out, then this is an indication that you were correct, there is sludge, but it just wasn’t enough to cause noticeable cold patches. In this instance, you would benefit from removing the sludge to prevent future issues. On the other hand, if you bleed your radiator, but it does not make a difference, again, you would benefit from flushing the system using the instructions below. Other signs that you need to flush sludge from your radiator include the boiler is making loud noises, and the heat pump is broken or leaking.

Checking Radiator

How To Flush A Radiator

The steps on how to flush a radiator are relatively straightforward; however, they do take care and patience to ensure that you do not damage your surroundings or the radiator itself. Follow our instructions below, and you will be able to remove radiator sludge successfully.

You will need:

1. Turn Off Your Central Heating

Whenever you are working on your radiator, you must ensure that you switch off your central heating and allow the radiators to cool down fully. This typically takes around half an hour but can be longer if you feel it is still slightly warm. When loosening the valves or removing the radiator from the wall, it is more than likely that you will come into contact with the water inside, so you do not want to run the risk of scolding your skin.

Turning Central Heating Off

2. Prepare Your Surroundings

Sludge inside your radiator isn’t pleasant, which means that you most definitely want to ensure that your surroundings are prepared before attempting this task. Be sure to spread towels or old sheets around the radiator, especially underneath the valves to protect your flooring.

3. Turn Off The Valves

The next step will be to disconnect your radiator from the rest of your system. To do this, you will need to start by turning off the thermostatic radiator valve (TRV), which is done by twisting the head to either the ‘0’ or ‘off’ position – they both mean the same, but which one you have differs on your radiator model.

On the other side of your radiator, you will find the lockshield valve. In order to turn this off, you will need to remove the plastic cap and then use a wrench or spanner to turn it clockwise all the way. When doing this, a handy tip is to count how many turns it takes you to turn off the valve; note this down as it will give you an indication on how to re-balance the radiators after flushing.

Turning Radiator Valve Off

4. How To Drain A Radiator

Now you have reached one of the most complicated steps, how to drain a radiator. Before doing this, always ensure that you have placed a bucket underneath the thermostatic radiator valve (TRV).

With a wrench or spanner in each hand, use one to grip the body of the valve and the other to begin loosening the nut between the radiator and the valve.

Next, using your bleed key, open the bleed valve to release any built-up air; at this point, you will begin to see water flow out and into your bucket. Using the same method as above, loosen the lockshield and then tilt the radiator to allow the remaining water to come out. Once emptied, use the key to close the bleed valve.

5. Flush The Radiator

Now that the water has been emptied, you can now move on to removing all of the sludge built up inside. Before doing this, you will need to completely disconnect the radiator from the wall and remove it from its brackets. As you would have already loosened the nuts on both valves, this should be relatively straightforward.

We would always recommend flushing the radiator outside but before doing this, do one last check to ensure that any excess dirty water is removed and into the bucket. The last thing you want is to carry the radiator through your home and leave a trail of mess along the way. You may even want to consider putting a plastic bag or towel around the inlets while you carry through to the garden.

Once in the garden, attach your hose pipe to the inlet of the radiator valve and switch the water on at full power, thoroughly flushing the inside. The pressure of the water should be enough to push out the sludge. If it is proving tricky to shift, then you can use a rubber hammer to try and dislodge any excess build-up. For those who are worried about damaging their garden with the sludge, we advise holding the radiator over a drain or placing a plastic sheet over the ground to collect the dirt.

Continue to flush out the radiator until the water that comes out of the inlet on the other side is completely clean.

Hose Pipe

6. Reconnect The Radiator

Once you have finished flushing the radiator and it is back inside, you can reconnect it using the above steps, but in reverse order. Be sure to re-tighten the nuts, open both valves and turn the lockshield valve the same number of times you noted down beforehand.

Finish by ensuring that you have opened the bleed valve to allow any air trapped inside to escape.

7. Check The Boiler Pressure

Now that you have flushed your radiator, there is one last task that we recommend, and that is to check the boiler pressure. Through disconnecting your radiator, the boiler pressure may have slightly dropped, so you will need to ensure that it is topped back up. At this stage, your central heating will still be turned off, so the pressure should be between 1 and 1.5.

Checking Boiler Pressure

How To Flush A Central Heating System

If you have flushed a radiator using the above steps but still find that your home is taking a while to heat up, then it is recommended to familiarise yourself with how to flush a central heating system. The first method, and the most straightforward, is to remove the sludge from each of your radiators. Cleaning each radiator individually is likely to take time but is a sure way to determine whether you need to speak with a professional plumber.

Having flushed each radiator, if you are still having problems with your central heating system, then we recommend getting in touch with our team. In this instance, you may need the system power flushing, and if this still doesn’t work, it is likely that there is a problem with the boiler itself. Our team are highly experienced in boiler installations in Milton Keynes and the surrounding areas, so we can diagnose the issue quickly, ensuring that disruption is minimised. If your boiler replacement has come unexpected, then we are able to offer installation on finance, allowing you to spread the cost with various interest-free options available.

Once your central heating system is back up to full health, then annual servicing will be essential to maintain its condition. We now offer a complete service plan, which ensures that your boiler is fully inspected and serviced, preventing the likelihood of future problems. This also provides you with priority access to our certified team, who are highly skilled in gas safety checks in Milton Keynes and much more.

Installing New Boiler

Restore The Performance Of Your Radiator

Should you notice that your radiators are no longer performing as well as they typically would, carrying out the necessary steps to determine an issue will be essential. The earlier than you can spot and rectify the problem, the less likely you are to run into bigger, more expensive repairs in the future. If you do have any radiator or central heating system-related issues and ensure whether they are serious, please do not hesitate to get in touch with our team. We are always more than happy to advise you on whether you can carry out DIY repairs or if you would benefit from a visit from one of our experienced plumbers.