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Plumbing Company london | Central Heating System Airlock: Understanding and Clearing Trapped Air

Sep 20


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A well-functioning central heating and hot water system is crucial for maintaining a comfortable and warm home. However, sometimes issues like airlocks can disrupt the efficiency of these systems. In this article, we will delve into what exactly an airlock is in a central heating and hot water system, and provide step-by-step guidance on how to clear trapped air in both heating and hot water systems.

Unbalanced heating system

An unbalanced heating system refers to a situation where certain areas or rooms in a building receive insufficient heat compared to others. This issue can lead to discomfort and uneven temperature distribution throughout the space. Unbalanced heating can occur for various reasons, such as improperly sized radiators, blocked or restricted pipes, or malfunctioning control valves. If you notice significant temperature differences between different parts of your home, it might indicate an unbalanced heating system. Addressing this problem usually involves adjusting radiator valves, ensuring proper pipe insulation, and seeking professional assistance to achieve a more consistent and comfortable indoor climate.

What is an airlock in a central heating and hot water system?

An airlock occurs when pockets of air become trapped within the pipes of the heating or water system. These air-trapped pockets hinder the circulation of hot water and heating fluid, leading to reduced performance, uneven heating, and even complete system failure. If not addressed promptly, airlocks can cause discomfort and inconvenience.

Signs and Symptoms of an Airlock

Airlocks in the heating or hot water system can manifest through various signs and symptoms, indicating the need for immediate attention. Uneven heating in radiators, where some remain cold while others are hot, is a common indicator of trapped air preventing proper water circulation. Gurgling or bubbling noises within the pipes and other radiators, are also telltale signs of airlocks. Reduced water flow from taps, as well as low water pressure, can result from airlock obstruction. If you notice any of these signs, it’s crucial to address the issue promptly to restore the efficiency and functionality of your heating or water system.



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Boiler Air Lock Symptoms

If your boiler is not producing hot water or radiators are not getting warm as they should, it could be due to trapped air hindering the proper circulation of water. Gurgling or hissing sounds coming from the boiler or radiators are often signs of airlock issues. Additionally, fluctuating water pressure on the boiler’s pressure gauge might point towards the presence of airlocks.

How to clear trapped air in a heating system?

Clearing trapped air from a central heating system involves a few straightforward steps:

  1. Turn off the System: Before you begin, ensure the heating system is turned off to avoid accidents or spills.
  2. Locate Bleed Valves: Find the bleed valves on your radiators. These small valves are usually situated at the top of the radiator.
  3. Prepare a Container: Place a container or cloth beneath the TRV to catch any water that may come out.
  4. Open the Valve: Using a radiator key or a flat-head screwdriver, gently turn the TRV anticlockwise to open it. You’ll hear a hissing sound as the trapped air escapes.
  5. Close the Valve: As soon as the water starts to flow consistently from the TRV, close it clockwise. Be cautious, as the water may be hot.
  6. Repeat the Process: Go through this process for all radiators in your system, starting with the lowest one and moving upwards.

How to Clear an Airlock in a Hot Water System?

To clear an airlock in a hot water system, follow these steps:

  1. Turn Off the System: Switch off the power supply to the water heater to ensure your safety.
  2. Identify the Taps: Locate the tap that seems to have the airlock issue. This could be a faucet with reduced or no water flow.
  3. Prepare a Cloth: Keep a cloth ready to catch any water that might escape during the process.
  4. Start with Cold Water: Turn on the cold water tap associated with the affected tap. This will help to force the trapped air out.
  5. Open the Hot Water Tap: With the cold water tap still running, open the hot water tap that’s experiencing the airlock. Allow the water to flow for a few minutes.
  6. Close the Taps: Once the water flows consistently, close both taps. You should notice an improvement in water flow.
  7. Repeat if Necessary: If the issue persists, you might need to repeat the process a few times to eliminate the airlock.

Airlocks in Central Heating Systems – MML Plumbing Ltd

At MML Plumbing Ltd, we understand the frustration and inconvenience that airlocks in central heating systems can cause. Airlocks disrupt the smooth circulation of fluids, leading to uneven heating, reduced system efficiency, and potential breakdowns. Our experienced team is well-equipped to tackle airlock issues efficiently and effectively. With years of expertise in plumbing and systems, we offer reliable solutions to clear airlocks and restore your plumbing system to optimal performance. Whether it’s bleeding radiators or addressing airlocks in pipework, our professionals are dedicated to ensuring your home remains warm and comfortable. Contact us to experience our top-notch services and expertise in resolving central heating system airlocks.



What to consider when picking heat pump radiators

Consider factors such as the radiator’s surface area, design, and the air source heat pump output capacity. Ensuring that the radiators are designed to work efficiently with the lower temperature output.

Variations of output temperature depending on your heating solution

The output temperature of radiators can vary based on factors like the operating mode, indoor air temperature, settings, and outdoor climate. It’s important to understand that the unit adjusts its output to meet your heating needs while maintaining energy efficiency.

Can heat pump systems work with a combination of radiators and underfloor heating?

Yes. This combination can heat pumps allows you to harness the benefits of both traditional heating systems and methods and create a well-balanced and efficient system for your home. Here’s how it works:


Radiators are a traditional method of heating that at high flow temperature can effectively provide quick bursts of warmth. However, radiators are more efficient when operating at lower temperatures, a high flow temperature which aligns well with the heat output of a heat pump. Consider modern panel radiators that are designed to work efficiently with lower-temperature water.



Underfloor Heating:

UFH is a more even and gentle solution that distributes warmth evenly across the upper floors of a room. This method operates at lower temperatures, making it an excellent match for heat pump systems. UFH can create a comfortable, warm and cosy environment while optimizing the house for energy efficiency.

Advantages of Combining the Radiator and Underfloor Heating:

1. Zoning: You can create different zones within your home, using radiators in some areas and underfloor heating in others.

2. Efficiency: Both hot water radiators and underfloor heating operate at lower temperatures, which maximizes the efficiency of your system. The heat pump doesn’t need to work as hard to produce the required warmth, resulting in less energy costs and savings.

3. Comfort: The combination of these two provides the house with a blend of quick warmth, low temperature, and consistent, gentle water distribution. This balance contributes to a comfortable house and warm living environment.

4. Design Flexibility: underfloor heating systems come in various styles and designs, allowing you to choose options while providing a comfortable home.

5. Comprehensive Solution: Underfloor heating can be particularly beneficial in rooms with larger floor areas, while the radiators upstairs can be effective in smaller spaces. The combination offers a comprehensive solution for different room sizes.

When combining underfloor heating with a heat pump system, it’s important to ensure that the system is properly designed and balanced.

Are radiators the best option to use with heat pumps?

It can be a suitable option to use with heat pumps, especially when chosen carefully. However, underfloor heating systems are often considered the best match for heat pumps due to their ability to distribute water evenly at the lower temperatures produced by heat pumps.

Can I use the radiator that is already installed in my home for heat pump systems?

Yes, however, here are some additional tips:

  • Heat pumps operate at lower temperatures than traditional gas boilers, so you may need to increase the size of your radiators to ensure that they can work effectively.
  • If your system is old and inefficient, you may want to consider an upgrade.
  • You will need to have our installer assess your existing radiators to determine if they are suitable for use with the unit.

Consult with MML Plumbing to get their advice on whether or not your home’s sufficiently existing radiators can be used with your old system.


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