How to Repressurise a Boiler: Step-by-Step Guide
If you’ve noticed your boiler pressure dropping, there’s no need to panic. It’s actually a common issue that many homeowners across the UK face. The good news is, it’s a relatively straightforward and quick fix that you might be able to do yourself.
The technician is demonstrating how to how to repressurise a boiler
In this step-by-step guide, we’ll walk you through:
- What causes a boiler to drop in pressure
- How to repressurise your boiler
- How long it takes
- When it’s time to seek professional help
- Boiler pressure FAQs
Let’s jump in and get your system back to full working order.
What Causes a Boiler to Drop in Pressure?
Before we dive into how to fix the issue, it’s important to understand what’s causing your boiler to lose pressure. There are a few common reasons your boiler pressure might be dropping:
- Leaks in the system. Small leaks, whether in the radiators or the pipework, can slowly cause a drop in pressure. Even if the leak is small, it can still impact the pressure over time.
- Bleeding radiators. If you’ve recently bled your radiators to remove trapped air, it can result in a pressure drop. This is particularly common in systems with older or more worn-out components.
- Faulty pressure relief valve. If the valve is stuck open or faulty, it can cause the system to lose pressure. If this is the case, get in touch with our boiler repair team.
- Expanding vessel issues. Over time, the expansion vessel in your boiler can degrade, which affects the system’s ability to maintain pressure.
Whatever the reason, low pressure can damage your heating system pretty quickly. Follow the steps below to fix your boiler today.
How to Repressurise Your Boiler: Step-by-Step
Step 1: Turn Off the Boiler and Allow It to Cool
Safety is always the top priority. Before you begin, make sure your boiler is off and allow it to cool for a few minutes. This helps prevent any burns or damage to the system during the repressurisation process.
Step 2: Locate the Filling Loop
The filling loop is a small, silver, flexible pipe. It’s usually located underneath your boiler and it connects the boiler to the mains water supply. If you can’t find it, check your user manual.
Not all boilers have a filling loop. If yours doesn’t, skip steps 3-6 and go straight to our alternative method below.
Step 3: Attach the Filling Loop (If Necessary)
If the filling loop is not already in place, you may need to attach it. Most systems will have a loop already connected, but in some cases, you might need to install one. Simply connect it to the two valves, ensuring the fittings are secure.
Step 4: Open the Valve to Allow Water Into the System
Now that your loop is secure, open the valve slowly to allow water to enter the system. Keep an eye on the pressure gauge (usually found on the front of the boiler) as you do this. You want the pressure to rise to the recommended level, typically around 1.5 bar. Some systems may recommend a slightly higher or lower pressure depending on the model, so always refer to your manufacturer’s instructions.
Step 5: Close the Valve Once the Pressure is Restored
Once the pressure has reached the ideal level, close the valve tightly to stop water from flowing into the system. It’s important to make sure the valve is completely closed to avoid any leaks.
Step 6: Turn the Boiler Back On
Now that the pressure is restored, it’s time to turn your boiler back on. Check the pressure gauge again to ensure the reading stays steady. If the pressure drops again after repressurising, you may have an underlying issue that requires an expert boiler service.
Alternative Method: How to Repressurise Without a Filling Loop
Not all boilers have a filling loop. If your boiler doesn’t have one, you’ll need to follow a different procedure.
This may involve using a different method of filling, such as connecting a hose directly to a cold water tap. You can refer to your boiler manual for specific instructions, or contact a qualified engineer if you’re unsure.
How Long Does It Take to Repressurise a Boiler?
Repressurising your boiler usually takes around 10-15 minutes, depending on how comfortable you are with the process. Once you’ve completed the steps, your boiler should be ready to run efficiently again. If you find the process too tricky or time-consuming, you can always contact a professional to handle it for you. You can read more about this in our article on servicing your own boiler.
How Much Does It Cost to Repressurise a Boiler?
If you’re tackling the task yourself, it won’t cost you a penny. If you need a professional to come out and repressurise your boiler (or inspect the system for potential issues), costs usually start around £85-100 per hour, depending on your location and the engineer’s rates.
At AddHeat, we charge £85 + VAT for the first hour. If we can repressurise your boiler in this hour (and no materials or parts are required), then that’s all you’ll pay.
How to Prevent Your Boiler Pressure from Dropping in the Future
To keep your boiler running smoothly and prevent pressure issues in the future, it’s important to have your boiler serviced every year. Annual servicing can help identify and fix small issues before they become bigger and more costly problems. For more on this, check out our guide to servicing your own boiler.
If you find that your boiler pressure continues to drop, or if you’re unsure about doing it yourself, don’t hesitate to contact us for a no obligation estimate.
Frequently Asked Questions (FAQs)
How Often Should I Repressurise My Boiler?
Repressurising is typically necessary when your system’s pressure drops below 1 bar. It’s not something that should happen regularly if your boiler is in good working condition. However, if the pressure drops frequently, it may indicate a more serious issue, such as a leak or a faulty valve.
Can I Use My Boiler While It’s at Low Pressure?
We don’t recommend that you use your boiler with low pressure. When the pressure is too low, your boiler will struggle to function properly, and it could potentially damage internal components. Always make sure the pressure is at the recommended level before switching your boiler back on.
What Happens if I Don’t Repressurise My Boiler?
If you don’t repressurise your boiler, it could stop working altogether. This means your heating and hot water won’t work, which can be particularly problematic in the winter. Additionally, leaving the problem unchecked may cause further damage to your system, leading to more expensive repairs down the line.
What Do I Do If I Can’t Locate My Filling Loop?
If you’re unable to locate your filling loop or if your boiler doesn’t have one, contact the boiler manufacturer for guidance. Alternatively, a qualified heating engineer can help you identify the best way to repressurise your system.