First Published: October 9, 2019. Updated: October 16, 2023
What is a Boiler Filling Loop?
A Boiler Filling Loop provides a temporary connection to the mains so that you’re able to repressurise and fill your heating system with water.
In this article, we’ll break down what a boiler filling loop is actually used for, and why they’re so important. Once you know how to repressurise your boiler using this small but useful component, you’ll save yourself a lot of headaches!
For information on related issues and other components in your heating system, you can also read some of the following blog posts:
Why do I need to repressurise my boiler?
There could be a few reasons that you need to repressurise your boiler, such as:
- Your boiler pressure has dropped below 1 bar
- You’ve recently bled your radiators
- You’ve got a small leak
- There’s a fault with the boiler itself
It’s helpful to know as much as you can about your Boiler Filling Loop. They play an important role in making sure your boiler pressure is at a reasonable level (around 1.4 bar), but if you don’t have the right knowledge, your boiler could be permanently damaged.
This is even more frustrating if it’s solved simply by repressurising the system. For detailed instructions on how you can repressurise your boiler, please watch the short video at the top of this guide >
How do you use a boiler filling loop?
Thankfully, even if you think you don’t know enough about how boilers and central heating systems work, using a boiler filling loop is a surprisingly easy task.
You’ll need one if your boiler pressure has dropped too much. Anything below half a bar will have a major effect on how your boiler operates. If it’s only recently been installed, your filling loop may be attached using blanking caps.
You won’t need anything else to repressurise your boiler, as you can just turn the filling loop valves using your hands. However, you’ll need to make sure that the valves are in the ‘off’ position before you start.
- Using your hands, make sure that the filling loop is fixed firmly into place
- Turn one valve so that it matches the direction of the pipe
- Slowly turn the other filling loop valve. Water will start coming through the mains and into your system
- Water should start to come through the system. As this happens, your boiler’s pressure displayed on the gauge should rise
- Once it hits 1.4 bar, close both of the valves back up
Some people find it more convenient to leave the filling loop attached or next to the boiler. This is actually against regulations, as they state your filling loop needs to be disconnected from your boiler when it’s not in use. If it’s left on, you can cause irreparable damage to your filling loop boiler. As well as this, it can be dangerous if you have children in the property. They can accidentally knock the filling loop valves, which would allow water to flow back into the system, raising the boiler pressure and cause more problems.
Why aren’t some filling loops connected to the boiler all the time?
Easy one, this. The connection between a filling loop and the boiler is temporary because water regulations strictly prohibit any water from flowing back into the mains. If you end up using the same water in your radiators as the water that comes out of the shower and taps, then you’ll be drinking from a highly contaminated source…not a nice thought!
In short, if you’re having to use the boiler filling loop often for repressurising, there might be a problem with your current boiler or your current heating system that needs fixing.
When a boiler is installed, the engineer should leave the filling loop easily accessible for you in case you need it to repressurise your boiler. If this isn’t the case however, boiler filling loops are relatively cheap to replace.
After a quick Google search, you’ll find that most services and online stores charge between £7-£20 for a new filling loop. Considering how this component allows you to repressurise your boiler, you’d be wise to make sure you have one at hand to use whenever you need it!
Your boiler’s filling loop will have at least one stop valve that is used to control the flow of water, and a double check valve that helps prevent the flow of water coming back through from the mains.
Why do I need to use my filling loop?
A filling loop’s function is to help you repressurise the boiler if your pressure is too low. However, this in itself is something you shouldn’t have to do too regularly.
If you think you’re having to top up your boiler too often – usually more than twice a year – then you might have problems like leaks in your system. There are a variety of areas that could be affected like pipes, radiators, or other parts of your heating system like expansion vessels or pressure release valves.
Regardless of the cause, your boiler shouldn’t be low on pressure all the time. You’ll have to find the leak as soon as possible before your boiler suffers more damage.
If you have to top up your boiler quite often, the oxygen that comes from the mains water supply will encourage further corrosion. This corrosion ultimately results in a build of sludge inside your radiators and pipes. When this occurs, your boiler will struggle to reach the right temperature and with corrosion and component degradation thrown into the mix, will give you far too many problems to deal with.
In short, if you’re having to use the boiler filling loop to repressurise quite often, it’s probably worth speaking to heating experts to get some friendly, reliable advice. You can do so by calling us directly on 029 2009 9898.