What is a pressure relief valve?
You probably don’t give your boiler much thought, or know much about the different parts inside. As well as the heat exchanger, expansion tank and circulator pump, there’s a small thing called a pressure relief valve. And it’s one of the most important parts. As the name suggests, the pressure relief valve plays a big role in regulating the pressure of your heating system, in particular stopping the pressure from getting too high and preventing dangerous situations.
What is the purpose of a boiler pressure valve?
Essential to keeping your boiler safe, pressure relief valves help stop pressure from building up. If your boiler didn’t have a pressure relief valve, it could lead to problems such as leaks or over-pressurising the whole system. It could even lead to more dangerous situation of the boiler exploding. Good job they’re all fitted as standard! The pressure valve comes into play when the boiler pressure gets too high – it opens to relieve the pressure and closes again once it’s back down to a safe level.
How does a pressure relief valve work?
If pressure builds up in a boiler, that’s when the pressure relief valve comes in to play. Here’s how they work in three simple steps:
- As the pressure builds, the resistant spring above the valve is forced to move
- This lets any hot water and steam escape via the outflow / discharge pipe
- When the pressure has dropped, the spring then pushes down to close the valve
What are the different types of boiler pressure valves?
The most common boiler pressure valves are pressure relief valves and safety valves. While they both do the same job, they work differently and are used in different systems.
Pressure relief valves are used in systems that use fluid or compressed air. They gradually open up when the pressure is rising so the system can return to its normal, stable level. Once that’s reached, the valve closes down. Boilers are sensitive systems, and need pressure relief valves to make sure they don’t over-pressurise.
Safety valves on the other hand work a bit differently. They don’t control the pressure to maintain it at the right level. Instead, they work to keep the system safe from disaster. So rather than opening gradually to release the pressure, a safety valve will fly open at speed to immediately release pressure. Safety valves play a big role in industries such as petrochemicals, pharmaceuticals, power plants and more.
What are the signs of a faulty pressure relief valve?
You may not be able to see the pressure relief valve as they could be in different locations depending on your heating system. However there are a few things you can look out for:
Leaks –water coming out from your boiler could mean that the pressure relief valve isn’t working as it should.
Noises – if you hear strange sounds, there could be an issue with your boiler pressure valve.
Error codes on the pressure gauge – these indicate a problem with pressure, that could be to do with the pressure valve.
What causes problems with pressure relief valves?
Blockages – dirt and debris could be clogging up the valve.
Corrosion – the pressure relief valve can rust over time – so it’s worth having it checked out – which our engineers will do on all boiler services.
If you’re concerned about your pressure relief valve or the condition of your boiler, we recommend you get a professional in. We have over 6,500 engineers across the UK, ready to help.
Top tips to maintain your boiler pressure valve
The best way to make sure your boiler pressure valve is maintained is to have your boiler serviced regularly. We can do a one-off boiler service to make sure everything’s running properly or you could take out HomeCare cover – which gives you a boiler service at no extra cost, and unlimited repairs should you ever need them.
You should not open up your boiler to see if your boiler pressure valve is working properly – you could end up damaging it. However, there are a few visual checks you can make:
- Check the discharge pipe for any leaks
- Keep the area around your boiler clean and clear from debris
- Get your boiler serviced regularly
If you notice any faults and want one of our engineers to take a look – please remember to record as much as you can on a smartphone or tablet. This will help us identify the fault quicker.
Want to know more about how boilers work and how we can help you find the right one? Just take a look at our guides.
Frequently Asked Questions
Where is the pressure relief valve on a boiler
You should find the pressure relief valve on the top or the side of your boiler – it’ll be connected to the hot water so look for pipes. If you’re not sure on where to look, you’ll find the details in your boiler’s manual (and if you can’t find that – just have a search online). Please remember though that the pressure relief valve could also be elsewhere – the airing cupboard, the loft – it all depends on the setup of your heating system. So while it could be at the top of your boiler, don’t take anything apart trying to look for it.
Where is the pressure relief valve on a combi boiler?
In most combi boilers the pressure relief valve is inside the boiler. If you’ve ever had repair work done, there’s the possibility it could have been moved to a different part, but it usually is inside the boiler.
How much is it to replace a pressure relief valve on a boiler?
Prices for a pressure relief valve can vary depending on the type of your boiler, along with installation costs. If you have HomeCare and need a replacement valve, you’ll only pay your excess – which could be zero – but not for any parts or labour.
What do I do if water is dripping from a boiler pressure relief valve?
You should check the area around the boiler and see if you can find out where the leak is coming from. It could be due to a faulty valve or excess pressure. You can check your boiler’s pressure gauge to make sure it’s within the normal range – which is usually between 1 to 2 bar. Another step you can take is to bleed your radiators to see if that helps reduce the pressure. However, the best bet is to get in touch with a professional who can fix it for you.
What is a boiler pressure relief valve discharge pipe?
The discharge pipe is a safety feature that’s connected to the pressure relief valve. When the pressure gets too high and the pressure relief valve opens, the excess hot water or steam comes out of the discharge pipe – away from the boiler to prevent damage or injury.