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Why Does My Boiler Sound Like an Aeroplane Taking Off?

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By Jay Singh

Is your boiler making noise like an aeroplane? It’s a sound that’s hard to ignore and certainly alarming, a loud roaring or whooshing from your boiler that sounds like a jet engine preparing for takeoff. While your boiler is a complex piece of machinery, this particular noise often points to a specific and serious issue: excessive pressure. If you hear this, it’s crucial to turn off your boiler and call a professional immediately. 

This loud noise is often a sign that your boiler’s internal pressure has become dangerously high. As a safety measure, the system is forcefully releasing this pressure, resulting in the “aeroplane” sound. In a recent case involving a Vaillant ecoFIT Pure 825, a technician diagnosed the problem as a failure of two critical components: the expansion vessel and the pressure relief valve (PRV). We can help you with these types of boiler problems as a leading boiler services company in London.

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We believe that your safety and the safety of your home is of utmost importance during a boiler service or any other gas appliance-related work. Our customer-first approach is what has allowed us to build up a stellar reputation over the last decade. The only way to ensure that your boiler or appliance is functioning efficiently and safely is with regular maintenance and professional servicing, which are usually carried out annually. There are a number of reasons to get a yearly service.

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The Culprits: Understanding the Key Components

To understand why this happens, it helps to know a little about the parts involved.

1. The Expansion Vessel

In a sealed central heating system, water expands when it’s heated. The expansion vessel is a small tank within your boiler designed to absorb this extra volume, keeping the pressure within a safe range. It’s divided by a rubber diaphragm; one side contains system water, and the other is filled with compressed air or nitrogen.

Over time, this diaphragm can rupture or degrade. When it fails, water floods the air-filled side of the vessel. Without the air cushion to absorb the expansion of the heated water, the pressure in the entire system can rise rapidly and exceed safe levels.

2. The Pressure Relief Valve (PRV)

The PRV is a crucial safety device, mandatory in all modern boilers. Its sole purpose is to protect the system from dangerous over-pressurisation. If the pressure inside the boiler exceeds a preset limit (usually around 3 bar), the PRV opens automatically to release the excess hot water and steam.

The loud “airplane” or roaring noise is the sound of this high-pressure mixture being violently discharged from the system through the PRV. While it’s a sign of a serious fault, it also means the safety valve is doing its job to prevent a more catastrophic failure.

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The Solution: A Job for the Professionals

When an expansion vessel fails and causes the PRV to operate, the solution is to replace both components. As demonstrated in the case of the Vaillant ecoFIT Pure 825, a qualified engineer will:

  • Safely drain the heating system.
  • Remove the faulty expansion vessel.
  • Replace the old Pressure Relief Valve.
  • Install the new components.
  • Re-pressurise the system to the correct level (typically between 1 and 1.5 bar when cold).
  • Thoroughly test the boiler to ensure it is operating safely and quietly.

Important: This is not a DIY job. Repairing or replacing these components involves working with the high-pressure and gas systems of your boiler. For your safety, this work must only be carried out by a Gas Safe registered engineer. Our team of professional gas engineers is ready to help you, Call Boiler Solutions.

Don’t Ignore the Warning Signs

A boiler that sounds like an airplane is a clear warning that it needs immediate attention. Other noises, such as gurgling, banging, or whistling (known as “kettling”), can also indicate underlying problems like trapped air or limescale buildup. Regular annual servicing can help identify and rectify these issues before they escalate.

If you’re concerned about any unusual noises from your boiler, don’t hesitate. For expert advice and emergency repairs, contact the team at Boiler Solutions today. Our certified engineers are on hand to diagnose the problem and restore your heating system to safe and efficient working order.

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