How do I repressurise my boiler?

Have you noticed your radiators aren’t as hot as they should be? Hot water taps keep having issues? This could mean your boiler pressure is too low and will need to be repressurised. 

While it’s not the end of the world, it’s important to regularly monitor your boiler pressure levels and we know this can be a daunting task for many homeowners without clear knowledge about how to go about it. We’re here to break it down and give you all the tips you need on how to identify low pressure, what to do about repressurising and how an engineer can help.

How to know if my boiler pressure is low

The first indicator that your boiler is having issues comes from hot water. You might notice showers aren’t reaching the temperatures you’d expect or you’re having trouble heating the house with radiators feeling colder than normal. Fortunately, there is an easy way to find out if your boiler pressure is low by checking the water pressure gauge on the front of your boiler. These are typically hydraulic gauges, however some modern boilers have digital gauges instead.

An ideal boiler pressure is between 1 and 1.5 but if you’re finding that your pressure levels are less than 1, it might be time to think about repressuring. While this is true of most UK boilers, some may differ slightly in their optimum range so be sure to check your boiler’s manual if you are unsure.

The causes for low boiler pressure can vary from home to home but there are two main reasons. Firstly, you could have a leak around your radiators or pipes causing a system-wide issue. There may even be damp patches in your boiler. Secondly, another common cause is bleeding your radiators which can cause a loss of boiler pressure as well. Luckily, the fix will be the same regardless of the cause in low pressure.

Is it safe to repressurise a boiler yourself?

If you’ve identified low pressure within your boiler, you can safely take on the task of repressurising a boiler without needing to call out an engineer. Within this guide, we have provided a step by step tutorial on how to increase pressure on your boiler for both standard and Worcester Bosch boilers.

However, there are some instances where you might need to call out an engineer. While a low pressure boiler isn’t risky to leave alone, it can damage your boiler’s efficiency over time which is why it’s important to have your boiler serviced as soon as possible. The cause of your boiler’s pressure may also prompt a visit to ensure the same issues don’t occur again.

How do I increase the pressure on my boiler manually?

Before you take on repressurising your boiler, make sure you’ve read through any manuals or guides on your specific boiler as certain steps may vary. Some boilers use an external filling loop that connects to your main water line and another to your boiler, while internal filling loops found in combi boilers are integrated into the system. Take note of which type of filling loop your boiler uses before continuing.

Now that you’re ready, here are the key steps you’ll need to follow:

1. Firstly, turn off your boiler, letting it completely cool down 
2. Lay down an old towel underneath to catch any water spillage that might occur
3. If you have an external filling loop (a flexible pipe with valves at each end), locate this and make sure that both ends are securely attached to the boiler’s pipes
4. Open up both valves to allow cold mains water to enter the system, 
5. Watch the pressure gauge carefully and close both valves once it reaches between 1 and 1.5 
6. Before turning the boiler back on, undo both ends of the external filling loop and remove it (again check that this applies to your boiler)
7. Turn the boiler back on and check the pressure again

While these steps will work for most boilers, Worcester Bosch boilers have a slightly different method for increasing the pressure on a boiler.

Here are the key steps for repressurising a Worcester Bosch boiler:

1. Lay an old towel underneath the boiler to catch any spills
2. Remove the hatch on the underside of your boiler and locate the internal filling key
3. Find the filling link, a small hole just to the right of a white square where the key will fit
4. Push the key into the link until the arrow on the key is close to meeting the black plastic
5. Until the arrow is facing you, turn the key anti-clockwise 
6. Allow cold water into the system by turning the white square clockwise
7. Check the water pressure and turn the square back to its original position once it reaches between 1 and 1.5 on the pressure gauge, this will shut off the water
8. Make sure the key is dried and place it back before putting the hatch on again
9. Switch the boiler back on and check the pressure again

How often should I check the pressure on my boiler?

We recommend checking the pressure on your boiler at least once a month to note any changes and make sure that the number stays between the 1 and 1.5 range. If you’re thinking of bleeding out your radiators, give your boiler another check as this is one of the main causes of low pressure.

What to do if the pressure doesn’t increase, or decreases quickly again?

If you’ve tried to repressurise your boiler and the heating issue persists, you shouldn’t keep trying. Instead, take a look at getting in touch with a heating engineer as there may be a leak or a damaged valve somewhere within your boiler.

Although you might be able to find the leak yourself, some damp spots will be located in areas that are complex to reach or dangerous without proper experience. This is why it’s crucial to reach out to a professional heating service as soon as you notice the pressure continue to decrease.

Custom Heat can support

There’s never a good time to lose your hot water and central heating, and when it happens it can disrupt your whole family. 

With Custom Heat, you can book a callout in just 2 minutes through our simple online booking system so your boiler can get up and running in no time. For peace of mind all year round, our Care Plans are designed to give you guaranteed same-day callout and an Annual Boiler Service from as little as £12.50 per month.

Get in touch with our expert heating engineers today.