How to stop the sound of dripping or trickling water inside your radiators

If you can hear water dripping or trickling inside your radiator, it’s very likely that your radiator is not full and contains air pockets. This is a common issue, especially in tall radiators, often because they are filled too quickly, causing air to be trapped. Here’s a comprehensive guide on how to resolve this problem.

If you feel you need a replacement valve, be sure to look at our radiator valves section.

Table of Contents

1. Understanding flow and return
2. Filling the radiator
3. Balancing the radiator
4. Signs of success
5. Other causes

Understanding flow and return

Radiators often have specific flow and return connections. The flow is the water coming into the radiator, and the return is the water exiting it. You can usually identify these connections by looking for arrows or the words 'Flow' or 'Return' near the connection points on the radiator. It’s crucial to ensure that these connections are correctly identified to maintain the efficiency of your heating system.

Bleeding your radiator

To get rid of the trapped air, you need to bleed your radiators. This process involves releasing the air to allow the radiator to fill completely with water. Bleeding radiators is essential for maintaining their efficiency and eliminating those annoying dripping or trickling sounds. 

Implications of trapped air

Reduced efficiency

Air in radiators prevents hot water from filling the entire radiator, reducing the heating efficiency of your system. This can cause radiators to feel cold at the top while being hot at the bottom.

Increased corrosion

Air in the system can lead to oxidation of metal parts, increasing corrosion and shortening the lifespan of your heating components.

Steps to bleed your radiator

1. Turn off the heating. Ensure your heating system is turned off to avoid any potential burns or water leaks.
2. Locate the bleed valve. The bleed valve is usually found at the top of the radiator.
3. Open the bleed valve. Using a radiator key, slowly open the valve. You will hear a hissing sound as the air escapes.
4. Close the valve. Once water starts to come out steadily, close the valve tightly.

• Further reading: The complete guide to bleeding a radiator

Filling the radiator

After bleeding, you need to fill the radiator again. This is how to do it properly:

1. Close the lockshield valve. Shut the lockshield valve to stop the flow of water.
2. Open the air vent. Fully open the air vent, which is usually on the opposite side of the flow.
3. Fill slowly. Fill the radiator very slowly, allowing the air to escape through the vent.
4. Check for water. When water starts coming out of the vent, it means the radiator is full. Close the vent and open the lockshield valve to fill the system.

• Further reading: How to fill a central heating system efficiently

Balancing the radiator

To ensure your radiator works efficiently, you need to balance it by setting the correct flow rate. This involves adjusting the lockshield valve to maintain a temperature difference of about 10-12°C lower than the flow side.

Steps to balance your radiator

1. Use a digital thermometer. Measure the temperature on the flow side.
2. Adjust the lockshield valve. Open or close the lockshield valve until the temperature is 10-12°C below the flow side.
3. Lock the valve. Once the correct temperature is achieved, lock the valve.

• Further reading: The complete guide to balancing a radiator

Signs of success

If you have successfully removed all the air, your radiator should be warm all over with no cold patches or sounds of trickling water. If not, you may need to repeat the process. For a completely balanced central heating system, the processes outlined above should be performed on all your radiators.

Other causes

Automatic air vents failing

Vertical radiators are often equipped with automatic air vents designed to release any accumulated air. These vents help ensure that your radiator remains fully functional and free from air pockets that cause trickling sounds. However, if these vents fail, air can build up within the radiator, leading to the annoying noises you're trying to avoid. Regularly checking these vents to ensure they are working correctly is crucial. If an automatic air vent fails, it might need cleaning or replacement to restore its function.

Fault radiator valves

Radiator valves control the flow of water into and out of your radiators. If these valves are not working correctly, they can allow air to enter the system or fail to seal properly, leading to air pockets and the associated noises. Ensuring that all radiator valves are in good working condition and properly adjusted is essential for maintaining a noise-free radiator system.

Need a replacement valve, or thinking of a different style? Check our range here, we have something for everyone.

• Further reading: The complete guide to how radiator valves work

Inadequate system pressure

If your central heating system's pressure is too low, it can lead to air being drawn into the system, causing air pockets in your radiators. Regularly check the system pressure and ensure it is within the recommended range. Most systems have a pressure gauge on the boiler, and maintaining the correct pressure can help prevent air from entering the system.

• Further reading: How to refill or repressurise a combi boiler