What is a pressure releasing valve and how do they work? Here we explain their function and what to do if a leak occurs.
A pressure release valve (PRV) is an important safety feature that helps to control the pressure levels within your boiler, ensuring that it does not get too high.
If your PRV is faulty, your boiler will usually shut down and present an error code on the interface.
If you’re wondering how to repair one and how they work, this troubleshooting guide is for you.
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What does a pressure release valve do?
A pressure release valve, pressure relief valve or PRV is a safety device used to let pressurised fluid exit a system safely.
This will avoid a dangerous accumulation of pressure which could result in a boiler shutting off or even rupturing entirely (which needless to say would be very dangerous).
PRVs open as a way of releasing pressure whenever it gets too high. Subsequently, they close when the pressure is back down to a safe level.
While they can be used in a wide range of appliances and settings (e.g., water heaters, the power generation industry, and the petrochemical industry), today we are focused on their use in domestic boilers.
These valves tend to be made from various materials, whether it be plastic, bras, aluminium or stainless steel.
In the case of spring-loaded PRVs, the spring is generally made from stainless steel.
Among the advantages of stainless steel is that it is more resistant to rust and therefore offers (on average) a longer lifespan before you’d need to have it replaced.
Where valves need to be light, however, aluminium would most likely be used.
How do Spring-Loaded Pressure Release Valves Work?
This type of valve consists of a spring, piston (used as a sensor), and a spring-loaded valve.
While pressure builds, the spring can be used to control the valve by ensuring that pressure (e.g., steam or hot water pressure) cannot pass through.
Once the force applied exceeds the pressure that the spring can take, the spring will move, and the valve will open releasing the pressure.
Once pressure starts coming down again, the spring will apply sufficient downforce to close the valve over again.
This smart mechanical approach can help keep your family and property safe.
Why Might a Pressure Release Valve Leak?
Please be aware that pressure release valves can suffer leaks. This might happen if the seal surrounding the valve has been worn down.
Alternatively, limescale or other accumulations of debris (e.g., rust) may be blocking the valve.
Moreover, blockages inside your heating system such as from dirt or debris could also prevent the PRV from closing as it should.
Either way, in order to have these issues fixed you’d need to hire a professional.
Please be sure to keep your heating system off when an issue like this arises until a qualified heating engineer can take a look and solve the problem.
The valve may need to be cleaned or even flushed, depending on the nature of the problem.
Also, whether or not there is an issue with your heating system (at this particular time), it’s advised that your heating system power flushed every 5-6 years.
This could prevent various issues including a leaking PRV.
If after having a PRV replaced (if this is required) and it still leaks, it may signal that there’s an issue with the internal expansion vessel of your boiler.
Again, you should hire a qualified heating engineer if this you suspect this is the issue as they’ll be able to find a suitable solution, which would likely involve repairing or replacing the internal expansion vessel.
How Long Do PRVs Last?
Pressure release valves usually last around 3-5 years before they need to be replaced.
Of course, their actual longevity will depend on the quality of the product and other factors such as how well they are maintained.
As for maintenance, you should have it tested as part of a boiler servicing once every year
Of course, if you spot the PRV leaking more often or if it frequently needs to be repaired, it’s probably beyond economical repair and in need of replacing.
Just as with having your boiler serviced, this must be done by a qualified heating engineer.
How to Replace a PRV on a combi boiler
If you suspect that the Pressure Relief Valve (PRV) in your combi boiler needs replacing, it’s essential to contact a Gas Safe registered engineer.
Before the engineer arrives, you should turn off the boiler to allow it to cool down.
The engineer will then drain the boiler until the pressure gauge reads zero. After that, they will replace the old PRV with a new one, ensuring it is correctly installed.
Once the new PRV is in place, the system will be refilled with water, and the radiators will need to be bled.
Finally, the engineer will check that the new PRV is functioning properly before completing the job.
Cost of Having a PRV Repaired or Replaced
If you find that your boiler’s pressure release valve needs to be repaired (e.g., it’s leaking) or it needs to be replaced, you might be wondering how much it would cost overall.
First and foremost, whatever the job, the average cost of hiring a qualified heating engineer is £30 to £60 per hour.
Here are the costs of having a PRV repaired/replaced by a professional and related jobs:
Repairing a pressure release valve
£30 to £120Replacing a pressure release valve
£70 to £190Fixing an internal expansion vessel
£30 to £120Replacing an external expansion vessel
£60 to £27Power flushing a heating system
£400 to £500Replacing a boiler
£800 to £2,800 *
If your boiler itself is beyond economical repair, it would be time to have it replaced.
Of course, for many households purchasing a boiler right now would be unfeasible.
With that said, thankfully, there are alternative ways of obtaining a new boiler without spending too much upfront.
For one, you could purchase a boiler on finance. In other words, you could buy now and pay later.
This may or may not include interest, but either way, buying on finance would let you keep your upfront expenses to a minimum.
Alternatively, you could take out a loan or use a credit. Regardless, you should not take on credit unless you are absolutely sure you can pay it back comfortably.
If you’re not sure if taking on credit is right for you at the moment, you might want to consider a boiler subscription.
A boiler subscription is a new model of obtaining a boiler. In this case you would effectively be renting a boiler for a fee.
However, this fee would get you more than just a boiler. Your subscription might also include an annual boiler service, zero call-out fees, or/and a modern smart thermostat among other additions.
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