The pressure relief valve is one of the most important safety components on a boiler. It plays a vital role in protecting the system from excessive pressure, which could otherwise result in equipment damage or even dangerous failures. If you’re responsible for maintaining a boiler or simply want to understand how your system works, knowing the location and purpose of the pressure relief valve is essential.
In this article, we’ll explain what a pressure relief valve does, how to locate it on a boiler, and why it’s so critical for safe and efficient operation.
What Is a Pressure Relief Valve?
A pressure relief valve (PRV), sometimes called a safety valve, is designed to automatically release pressure from the boiler if it rises above a certain limit. This prevents the internal components from being subjected to excessive stress, which can lead to ruptured pipes, leaks, or catastrophic failure.
Boilers generate pressure as water is heated and converted into steam or hot water for distribution throughout a building or industrial process. If something goes wrong—such as a thermostat failure, blocked pipework, or pump malfunction—pressure can build up rapidly. The pressure relief valve ensures the system remains within safe operating limits by venting excess pressure to the atmosphere.
VALSTEAM ADCA Pressure Reducing Valves
The ADCA PRV41SS is a compact, direct-acting pressure reducing valve with spring-loaded piston sensing and a balanced plug design. It is ideal for regulating compressed air and other gases in small to medium systems, ensuring precise and stable downstream pressure. Constructed from stainless steel, it offers excellent durability and corrosion resistance in demanding environments.
For larger applications, the ADCA PRV57 is a pilot-operated pressure reducing valve designed for use with steam, compressed air, nitrogen, and other gases. Its robust design, available in carbon or stainless steel, provides reliable performance in high-capacity systems where accurate control and efficiency are critical. Both valves are engineered to safeguard equipment and maintain consistent pressure across a wide range of industrial processes.
VALSTEAM ADCA | PRV41SS PRESSURE REDUCING VALVES
VALSTEAM ADCA | PRV57 PRESSURE REDUCING VALVES
Where Is the Pressure Relief Valve Located on a Boiler?
On most boilers, the pressure relief valve is found on the top or side of the boiler unit. It is usually attached to the boiler’s main body where the water or steam is pressurised. You can identify it as a small, round valve housing with a discharge pipe connected to it.
The discharge pipe leads away from the valve and is directed downward or toward a drain. This pipe ensures that any released water or steam is safely channelled away from the boiler and surrounding area. In domestic boilers, the pressure relief valve is often located near the expansion vessel, while in larger industrial systems, it may be positioned close to the main drum or pressure vessel.
Here’s how you can identify it:
Appearance: A compact valve body, often with a lever or test knob on the top.
Pipe Connection: A pipe runs from the valve to a safe discharge point.
Markings: Some valves are labelled with their set pressure (e.g., “3 bar”), indicating the pressure at which they will open.
Why Is the Pressure Relief Valve Important?
The pressure relief valve is a crucial safeguard in both residential and commercial boiler systems. Without it, any fault that leads to overpressure could result in serious damage or injury. The valve ensures that:
Excessive pressure is vented safely.
Boiler components such as heat exchangers and pipework are protected from rupture.
The system remains compliant with UK safety regulations and standards.
In many cases, boilers are fitted with multiple layers of protection, including temperature controls and expansion vessels. However, the pressure relief valve acts as the final line of defence against overpressure.
Common Signs of Pressure Relief Valve Issues
It’s important to inspect the pressure relief valve regularly, as issues can develop over time. Some common signs of a problem include:
Constant Dripping or Leaking: Indicates that the valve may not be sealing properly.
Discharge of Water or Steam: If the valve releases fluid when the boiler is operating normally, the system pressure may be too high, or the valve may be faulty.
Corrosion Around the Valve: Can affect its ability to function correctly.
If you notice any of these issues, the valve should be inspected by a qualified engineer immediately.
Maintaining and Testing the Pressure Relief Valve
Regular maintenance is essential for keeping the pressure relief valve in good working order. Engineers may perform the following checks during routine servicing:
Testing the valve manually using the test lever to ensure it opens and reseals properly.
Inspecting for signs of wear, corrosion, or deposits.
Checking the boiler’s pressure gauge to ensure system pressure remains within normal limits.
In industrial applications, pressure relief valves are subject to strict testing schedules under UK regulations such as the Pressure Systems Safety Regulations 2000 (PSSR).
High-Quality Valves for Boiler Systems
At ISIS Fluid Control, we supply a wide range of pressure reducing valves and safety valves designed for use in steam and water systems, including boilers. Our products are engineered to deliver precise control and dependable protection, ensuring your system operates safely and efficiently.
Whether you are managing a domestic heating system or a large industrial boiler, our team of experts can help you select the right valve for your application and provide guidance on maintenance and adjustments.
Keep Your Boiler System Safe and Reliable
The pressure relief valve may seem like a small component, but its role in safeguarding your boiler system cannot be overstated. Knowing where it is located and how it works is an essential step towards ensuring the longevity and safety of your system.
If you need advice on selecting or maintaining a pressure relief valve, contact ISIS Fluid Control today to speak with one of our technical specialists.