downstairs radiator bleeding

In this article, we’ll talk about the most common reasons why radiators don’t heat, as well as the other problems that can happen. Our heating engineer will answer questions that are often asked about these radiator issues too.

Why is my radiator not getting hot but the pipes are?

There are several reasons why your radiator might not be getting hot even though the pipes are. One common cause is air trapped within the system. This stops the hot water in the radiator from moving around properly, so it stays cold. To resolve this, you need to bleed the radiator till it’s hot enough.

Bleeding involves releasing the trapped air by opening the radiator’s bleed valve using a radiator key.

This should allow the hot water to flow freely and heat the radiator. After you bleed the radiator hot enough, you also have to fill the system through the top-up valve to 1 bar.

Why is my radiator on but not heating up?

If your radiator is on but not supplying heat, air accumulation or sludge buildup might be the issue, which can create cold spots within the radiator, while sludge can obstruct the water flow.

Bleeding the radiator will release the air pockets, while flushing the heating system can remove sludge and debris, enabling efficient heat transfer.

Another issue can be that the combi boiler pump is not working and you need a gas-safe registered engineer from MML Plumbing who can check this issue.

Why is my radiator completely cold at the bottom when the heating system is on?

The reason for this issue in the radiator is the sludge build-up on the bottom part. Another issue can be the circulating pump fault, a blocked thermostatic radiator valve, or a problem within the central heating system pipes.

First, check if the valves are open and the pump is functioning correctly. If these are fine, it’s advisable to consult our gas-safe registered engineer to diagnose and fix the more complex issues within the system.

Why is my radiator not heating up despite being bled?

The issue may lie deeper within the heating system. There might be a blockage in the pipes preventing properly heated water from circulation. Additionally, the thermostat might be faulty, preventing the boiler or heat pump from sending hot water to the radiator.

What do you do when just one radiator is cold at the top?

When only one radiator is cold while others are working fine, it’s likely an isolated issue. Start by bleeding the cold radiator to release the air. If this doesn’t help, check the radiator valves, and ensure they are fully open.

If the problem persists the heating system needs to be rebalanced by supplying each radiator the same amount of heat. This can be done by turning down the lockshield valves a few turns starting the first more than one radiator which is closest to the boiler.

Then I worked towards the end. The closest radiator lockshield valve to the boiler needs to be turned almost fully down while the futures valve has to be almost fully open.

What happens if you bleed a radiator with the central heating system on?

Bleeding a radiator with the heating on is not recommended. The system is pressurized and hot, so opening the bleed valve can result in hot water and steam spewing out, causing burns to your skin.

Another problem that can arise when the system pressure drops is that the boiler heating pump will run dry and it will burn out.

Always turn off the boiler and allow the system to cool before bleeding a radiator.

How am I get rid of sludge in my radiator?

To get rid of sludge in a radiator, you’ll need to power flush the central heating system. Flushing involves using a specialized machine to circulate water and cleaning agents at high pressure to remove the sludge and debris from the system.

A qualified heating engineer should carry out this process for effective results.

If you would like to wash the radiators yourself, you can do this by using high-pressure clean water. This might improve the radiator performance a bit.

Why is my radiator cold even after bleeding?

If a radiator remains cold after bleeding, there may be a more significant issue, such as a blockage deeper in the system or a malfunctioning component.

It might also indicate a problem with the system water pressure or the pump. Seeking professional assistance from MML Plumbing is recommended to diagnose and address any radiator problem.

Reach out to us for any concerns related to your radiators.


Why is only one radiator not working?

A single radiator not working could be due to localized issues, such as trapped air, a closed radiator valve, blockage or an unbalanced system.

Begin by bleeding the radiator and ensuring the valve is fully open. Also, it is possible to remove the TRV head and push down the pin to unblock the stuck radiator valve.

If the problem persists, there might be a more complex problem within the radiator or the pipes supplying it.

Why are all my radiators not working correctly after bleeding?

If all radiators stop working after bleeding, you may have a low water pressure in the system. Radiators need sufficient pressure to function properly.

Check the boiler pressure and gauge on the boiler – if it’s below the recommended level which is 1 Bar, you may need to repressurize the system following the manufacturer’s instructions.

If you still have the issue after stopping up the system, the boiler has a fault that needs to be checked out.

radiator install

How do you fix a cold central heating radiator?

Fixing a cold heating radiator requires identifying the root cause. Begin by bleeding the radiator. If this step doesn’t resolve the issue, examine the thermostatic radiator valve and confirm it’s completely open.

If the problem persists, consider the possibility of system blockages and the potential need for chemical flushing.

How often should you bleed radiators?

You should bleed your radiators annually for your heating system’s maintenance routine. This will help prevent the buildup of sludge and ensure efficient heat distribution.

Here are some safety tips to keep in mind when bleeding radiators:

  • Make sure that the boiler is turned off before you start bleeding the radiator.
  • Wear gloves and eye protection to protect yourself from hot water and steam.
  • Do not over-please the radiator, as this can damage the radiator.
  • If you are not comfortable bleeding the radiator yourself, call a professional plumber.

Can a noisy radiator cause heat not to work?

Yes, a lousy radiator can indeed cause the central heating system not to work effectively. A malfunctioning radiator with air trapped or blockages can impede the circulation of hot water, reducing overall heat output.

Proper maintenance and timely repairs are crucial for the efficient operation of your whole system, however.

How can I tell if my radiator is clogged?

  • The radiator is cold or has cold spots: it is a sign that there may be a blockage or circulation problem.
  • The radiator makes gurgling or banging noises: which can be a sign of a blockage in the radiator.
  • The radiator is not warming up as quickly as it used to: this may be a sign of a blockage.
  • Radiator leak: This may be a sign of rust inside the radiator.

If you notice any of these signs, it is a good idea to have the radiator checked by a qualified plumber.

radiator installed by our plumber

How to know if I need a new radiator?

You might need a new radiator if your current one is corroded, leaks persistently has cold spots despite bleeding, or is incompatible with modern heating systems.

Which radiator to bleed first?

Start bleeding all the radiators up on the upper floors and work your way to the downstairs radiators. This is because air tends to accumulate in the higher parts of the system.

Begin with the radiator farthest from the boiler and then proceed to the closer ones.

Here are the steps involved in bleeding a radiator:

  1. Turn off the boiler.
  2. Locate the bleed valve on the radiator. It is usually a small, screw-type valve located at the top of the column radiator.
  3. Put the radiator key into the bleed valve and turn it anticlockwise until a small amount of water starts to drip out.
  4. Once the radiator bleed, close the bleed valve.

Can bleeding radiators affect the boiler?

Bleeding radiators should not significantly affect the boiler. However, if bleeding results in a substantial drop in system pressure, the boiler might shut down as a safety measure.

After every radiator bleeding the system needs to be repressurized.

Do you need to bleed all radiators or just one?

It’s a good practice to bleed all radiators in your home. Even when one radiator not working, bleeding all radiators ensures balanced pressure and optimal heat distribution throughout the system.


Why is my radiator lukewarm?

A lukewarm radiator could be due to blockage preventing proper circulation of the water. Bleeding the radiator will help release the trapped air and restore its efficiency.

Do plumbers deal with radiators?

Yes, our plumbers often deal with radiators and central heating systems. We can perform maintenance, repairs, and installations to ensure your system functions properly.

Do you let all the water out when bleeding a radiator?

No, bleeding a radiator doesn’t involve letting all the water out. You’re only releasing a small amount of air that has accumulated at the top of the radiator. The little water that will come out from the radiator, you can catch it with a towel.

How do you unblock a central heating radiator?

To unblock a radiator, you might need to power flush the system using specialized equipment. Flushing involves sending high-pressure water through the system to dislodge and remove blockages.

How do plumbers flush radiators?

Plumbers can flush radiators using a flushing machine. This machine connects to the central heating system and circulates water and cleaning agents at high pressure to the radiator’s heating dislodge and remove sludge and debris from upstairs radiators.

Do flushing radiators work?

Yes, flushing radiators can effectively address issues related to sludge, debris, and blockages within the central heating system.

Over time, rust, sediment, and other contaminants can accumulate in the radiators and pipes, hindering the efficient flow of hot water and reducing the overall performance of the central heating controls and system.

Flushing radiators, especially through a process called flushing, can help remove these deposits and improve the’s functionality. Flushing involves using a specialized machine to circulate water in the system.

Here’s how it works:

1. Preparation: The gas-safe registered engineer will isolate the radiator being flushed and connect the flushing machine to the radiators.

2. Circulation: The machine will circulate a mixture of water and cleaning chemicals through the radiator and pipes at high speed. The strong flow helps break down and dislodge the deposits.

3. Disposal: The dislodged debris is then flushed out of the system through a drain valve.

4. Refill: Fresh water is introduced into the system to flush out any remaining cleaning agents and debris high-pressure system.

Power flushing can often result in noticeable improvements in radiator performance. After the process, radiators tend to heat up more evenly, and the overall radiator heating efficiency of the system can be restored.

This can lead to better heat distribution, reduced energy consumption, and a more comfortable indoor environment.

Can I flush my radiator myself?

While it’s technically possible to flush a radiator yourself with clean water by filling the radiators through a garden hose, power flushing requires specialized equipment and knowledge. It’s recommended to hire a professional to ensure proper and effective flushing.

How long should you bleed a radiator for?

When bleeding a radiator, you should open the bleed valve until a steady stream of water flows out without any hissing sound. This usually takes a few seconds to a minute per radiator.

Why are two of my radiators cold?

Two cold radiators could indicate sludge in the pipes connected to those cold radiators downstairs. Bleeding them might help, but if the issue persists, a more comprehensive assessment might be necessary.

How long should radiators take to heat up?

The time it takes for radiators to heat can vary based on several factors, including the radiator size, the property insulation, the flow water temperature in the heating system, and the overall efficiency of the system.

In general, you can expect radiators to start emitting heat within a few minutes to half an hour after the boiler is turned on.

For smaller rooms and radiators, you might notice heat within 5 to 10 minutes. Larger rooms or radiators might take closer to 30 minutes or even an hour to reach their full heating potential.

Keep in mind that the initial warmth might be subtle and gradually increase as the radiator heats the surrounding room.

If your radiators are consistently taking an unusually long time to heat up or are not reaching the desired temperature, there could be underlying issues such as trapped air, blockages, or a faulty boiler pump.

Radiator Repair And Installation

Explore Comprehensive Radiator Services with MML Plumbing Ltd.

Considering a new radiator installation, boiler install, maintenance, or repair? Our professional engineers at MML Plumbing guarantee seamless and effective radiator installations, delivering consistent hot water and comfortable heating. Embrace the advantages of a new radiator. Get in touch today!