6 Easy Steps to Repressurise a Boiler and Fix Low Boiler Pressure

by | Heating

Originally published: November 25, 2023
Last Updated: April 30, 2024

Reading time: 7.085 minutes

Disclaimer

plumbinghub.info is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com, amazon.co.uk, amazon.ca or amazon.it.

Hey there! Feeling the heat because of low boiler pressure? No worries, we’ve got your back! In this article, we’ll show you the easy steps to repressurise your boiler and fix that pesky problem.

If you’ve noticed that the water pressure gauge on your boiler is below 1 bar, it’s time to take action. Just follow our simple instructions, and you’ll have your boiler back up to optimal pressure in a jiffy.

First, find the external filling loop on your specific boiler model. Then, switch off the boiler and let it cool down (This bit is optional, but hot heating systems will already be at a higher pressure than cold ones). Open both valves on the filling loop to let cold water enter the system. Keep an eye on the pressure gauge and close the valves when it reaches 1.5 bars.

Finally, switch the boiler back on, and you’re good to go. Remember, if you encounter any high-pressure issues, it’s best to seek help from a qualified engineer.

Let’s get that pressure up and keep your home toasty warm!

Key Takeaways

  • Regularly checking the pressure gauge ensures the stability and efficiency of the boiler.
  • Low boiler pressure can lead to reduced heat output and inefficient operation.
  • Repressurising the boiler with a filling loop is a simple and effective method.
  • If the pressure keeps dropping after repressurising, there may be an underlying issue that requires professional assistance.

Step 1. Check the Water Pressure Gauge

Boiler Pressure Gauge

To check the water pressure gauge on your boiler, start by ensuring that it’s below 1 bar. The water pressure gauge is an essential component that indicates the pressure level within your boiler system.

If the gauge reading is below 1 bar, this signifies low boiler pressure, which can lead to inefficient heating and potential damage. To address this issue, you need to repressurise your boiler.

Step 2. Determine if your system pressure is low

To determine if your boiler pressure is low, you’ll need to check the water pressure gauge on your boiler. Here are the steps to follow:

  • Locate the water pressure gauge on your boiler.
  • Observe the gauge and check the reading.
  • If the reading is below 1 bar, your boiler pressure is too low.
  • Low-pressure issues can cause heating and hot water problems.
  • It’s important to address low pressure promptly to restore functionality.

If you find that your boiler pressure is below 1 bar, you’ll need to repressurise it.

Step 3. Switch off the Boiler and Let It Cool

To begin the process of repressurising your boiler and fixing low boiler pressure, first, switch off the boiler and allow it to cool for a period of 4 to 6 hours. This step helps you get an accurate reading as hot heating systems will be at higher pressure. However, it isn’t completely necessary.

Allowing the boiler to cool down is a safety measure before re-pressurising it. It reduces the risk of burns or scalds when working near it.

Step 4. Open Both Valves on the Filling Loop

Filling Loop

To open both valves on the filling loop, locate the valves and turn them counterclockwise. This will allow cold water to enter the system and help repressurise your boiler.

Here are some important steps to follow:

  • Find the filling loop valves on your boiler. They’re usually located near the boiler or on the pipework.
  • Turn both valves counterclockwise to fully open them. This will allow water to flow into the system.

Boiler manufacturers like Worcester Bosch might have the filling loop built in. Some of these require a separate key, so you may need to check your manufacturer’s instructions.

Step 5. Close the Valves Once Pressure Reaches 1.5 Bar

Once the pressure gauge reaches 1.5 bar, promptly close the valves to maintain the ideal boiler pressure and prevent over-pressurisation. Closing the valves at this point will ensure that the pressure remains within the recommended range of 1-1.5 bars.

Here are some key points to keep in mind when closing the valves:

  • Monitor the pressure gauge closely to know when it reaches 1.5 bars.
  • Close the valves promptly once the pressure stabilises at 1.5 bars.
  • Avoid delaying the closing of the valves to prevent the pressure from exceeding the recommended limit.
  • If you over-pressurise, then it is likely the boiler’s pressure relief valve will open to protect it, depending on how the boiler is installed, you may see this water going through a tundish before going to the drain.

Step 6. Switch the Boiler Back on

Switch

After closing the valves to maintain the ideal boiler pressure, you can now switch the boiler back on.

Wait for the boiler to ignite and start heating the water. It’s important to monitor the boiler and check if the pressure remains stable.

If the pressure drops again quickly, and you need professional assistance, contact a qualified gas-safe boiler repair engineer.

Taking these steps will help repressurise your boiler and fix low boiler pressure in a safe and efficient manner.

Repressurising With a Filling Key

Worcester Fill link keys

You can easily repressurise your boiler using a filling key. Here are the steps to follow:

  • Insert the filling key into the key manifold keyhole to repressurise the boiler.
  • Rotate the key counterclockwise until you can see the system is filling.

Keep an eye on the pressure gauge until it reaches 1.5 bars. Once the pressure reaches 1.5 bars, turn the key to maintain the pressure.

Repressurising your boiler with a filling key is a simple and effective way to fix low boiler pressure. Just remember to follow these easy steps and monitor the pressure gauge closely.

If you have a Worcester boiler, they made two different types of key, as you can see above, if you aren’t sure which one you need, you can easily buy a pair from Amazon.

Repressurising With an External Filling Loop

To repressurise your boiler using a filling loop, follow these steps:

  1. Switch off the boiler and let it cool down.
  2. Locate the filling loop, usually an external pipe connected to the boiler.
  3. Check that both valves on the filling loop are closed.
  4. Open both valves slowly, allowing cold water to enter the system.
  5. Keep an eye on the pressure gauge.
  6. Close the valves once the pressure reading reaches 1.5 bars. Do not exceed this level to avoid damaging the boiler.
  7. Once the valves are closed, switch the boiler back on.
  8. Check the pressure gauge again to ensure it remains stable.

Repressurising your boiler with a filling loop is a simple and effective way to fix low boiler pressure.

Frequently Asked Questions

How Do I Fix Low Pressure on My Boiler?

To fix low pressure on your boiler, first check the water pressure gauge. If it’s below 1 bar, repressurise it. Follow the manufacturer’s instructions, but typically you’ll need to use an external filling loop. Switch off the boiler, open both valves on the filling loop to let cold water in, close them at 1.5 bars, and switch the boiler back on.

Can I Repressurise My Boiler Myself?

Yes, you can repressurise your boiler yourself. Check the water pressure gauge, and if it’s below 1 bar, follow the manufacturer’s instructions. Generally, you’ll need to use the external filling loop. Switch off the boiler, open both valves on the loop, close them at 1.5 bars, and switch the boiler back on.

How Long Does It Take to Pressurise a Boiler?

It typically takes less than a minute to repressurise a boiler after it has been switched off and cooled down.

Is low boiler pressure dangerous?

Low boiler pressure is not inherently dangerous, but it can cause issues with the performance and functionality of the boiler. It will ultimately lead to the boiler shutting down altogether. It is important to address low boiler pressure promptly to ensure the proper functioning of the system.

What happens if your boiler pressure is too high?

If the boiler pressure is too high, it can lead to various problems. The pressure relief valve may release excess pressure, causing water to leak from the system. This can result in damage to the boiler and surrounding components, but normally won’t as it should discharge to a drain or outside wall. 

What causes a boiler to drop in pressure?

There are several potential causes for a boiler to drop in pressure. Common reasons include leaks in the heating system, such as a faulty pressure relief valve or expansion vessel, a leaking radiator valve, or a damaged pipe. Additionally, bleeding radiators or venting air from the system can also cause a drop in pressure. It is important to identify and fix the source of the pressure drop to ensure the boiler operates efficiently.

Disclaimer

plumbinghub.info is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com, amazon.co.uk, amazon.ca or amazon.it.

About Nick Jolliffe

With over two decades of experience in the Plumbing and Heating industry, Nick has become a trusted expert in the field. He has developed an impressive product knowledge across all aspects of plumbing and heating, including renewables, making him the go-to person for advice and product recommendations for any plumbing application. Whether you're a tradesperson or a DIY consumer, you can trust Nick to provide you with the right solution for your plumbing needs.

Our recent articles

Best Mixer Showers In 2024

Mixer showers are a staple in UK bathrooms, seamlessly blending hot and cold water to provide a comfortable shower experience. From dual-outlet models to minimalist designs, these showers vary in size and style. While a good shower can elevate your morning routine, a...

Everything You Need to Know About Sump Pumps

You might think that a sump pump isn't necessary if you've never had water issues before, but don't let past luck lull you into a false sense of security. If you live in an area even remotely susceptible to heavy rains or flooding, it's essential to get acquainted...

Victorian Plumbing acquires Victoria Plum for £22.5m

In a major move to accelerate its growth, Victorian Plumbing, the UK's leading bathroom retailer, has acquired Victoria Plum, an online-only bathroom retailer, for £22.5 million. The acquisition, announced on May 17, 2024, marks a significant strategic milestone for...

Latest in Heating

4 Best Oil Filled Radiators – 2024 Buyer’s Guide

Just as the chill of the season starts to seep into your bones, you're probably considering how to keep your space snug without sending your energy bills through the roof. You've heard about oil filled radiators and their reputation for efficiency and sustained...

Troubleshooting Common Radiator Problems: Fix Cold Radiators Fast!

You're facing a cold front inside your home, as frustrating as a puzzle missing its final piece when your radiators won't heat up properly. Don't let the chill set in; you've got the power to diagnose and mend common radiator woes swiftly. By understanding the typical...

How Long Does a Boiler Last? When to Replace Your Boiler.

In our homes, boilers are the unsung heroes, silently working to keep us warm and cozy. But like all appliances, they have a limited lifespan. Knowing when to replace your boiler can save you from facing unexpected breakdowns and costly repairs. In this post, we will...

The Future of Heating? Hydrogen Boilers – What You Need to Know

Are you interested in a potential replacement for natural gas to heat your home? Looking for a more sustainable and eco-friendly alternative? Look no further! Hydrogen-ready boilers have the potential to replace traditional gas boilers and reduce carbon emissions....

0 Comments

Submit a Comment

Your email address will not be published. Required fields are marked *


The reCAPTCHA verification period has expired. Please reload the page.

Don't miss out! Sign up to get the latest news, guides and product special offers!

Sign up to the Plumbing Hub Newsletter. We'll send you an email once or twice a month, with the latest news, product guides, and special offers on products. Join our mailing list to receive the latest news and updates from our team.

You have Successfully Subscribed!