What does a pressure relief valve do?

In order for your boiler to efficiently provide heat and hot water to your home, it needs to maintain the right balance of water and gas. There are many different components within a boiler that ensure it operates correctly and safely, one of which is a pressure relief valve. In this guide, we’ll be exploring what a boiler pressure relief valve is and the role it plays within your heating system.

What is a pressure relief valve and what does it do?

The main role of a pressure relief valve (also referred to as a safety release valve) is to prevent excessive pressure build-up. It works by opening and rerouting some of the pressurised fluid when the pressure starts to rise excessively, and then shuts once the pressure has reduced to a secure level. If the pressure relief valve does not operate correctly, the boiler’s internal pressure can escalate to potentially dangerous levels, leading to a full system shutdown to prevent a serious incident.

The valve can normally be found inside the boiler casing at the bottom. There are various types of valves that work in different ways, the most common type for boilers are spring-loaded relief valves. So, when too much pressure pushes on a resistant spring, the valve will open and create space for the pressure to escape. When the pressure is released, the spring pushes back down and closes the valve.

What are pressure relief valves made of?

PRVs can be made from several different materials including aluminium and brass or plastic and stainless steel. The spring within the valve is usually made from stainless steel as it is not as likely to rust compared to other materials. Therefore, it should have a fairly long lifespan without the need for replacement. However, in some instances the valve might need to be lighter in weight, in these cases, aluminium is used instead of steel.

What causes a pressure relief valve to leak?

If you’re going to encounter a problem with your PRV it is likely to be a leak. Leaks can have multiple different causes such as the seal around the valve eroding or the valve itself becoming blocked with limescale or debris. If there is a blockage in your valve, it might prevent it from closing properly, but if it is cleaned or flushed by an experienced engineer that could be enough to solve the issue without need a replacement. It is also recommended that you get your heating system cleaned out, or the valve could quickly become blocked again.

If you have your relief valve replaced and there is still a leak, it could be that you have a problem with your boiler expansion vessel. The job of the expansion vessel is to provide space where excess water can go when the system is heating up to relieve pressure on it. So, if your boiler pressure is getting too high and you don’t have an issue with your pressure relief valve, it could be that it is your expansion vessel that isn’t working as it should. A qualified engineer will be able to confirm the cause of the leak for you.

How often should pressure relief valves be replaced?

Your engineer should test the valve every time you have a boiler service, which is normally every 12 months. If there are no issues with the valve, it should have a lifespan of between three and five years. It might require replacement sooner than this if you find that it is leaking frequently and has needed a few repairs to remain operational.

Buy from boiler spare parts suppliers online

If you need a replacement pressure relief valve for your boiler, National Boiler Spares can help. As specialists in new and refurbished boiler spares and parts, we have a wide range of parts to fit many different boiler brands and models. Explore our full shop online today and get fast delivery direct to your door. Contact us if you have any questions.