What are boiler filling loops & how to use them?
The Boiler Filling Loop is a temporary connection to mains that allows you to repressurise your heating system and add water.
In this article, we will explain what an external boiler filling loop is used for and why it’s so important. The boiler’s filling loop is a temporary connection to mains that allows you to repressurise your heating system and add water.
This small but very useful component will save you a lot of time and headaches and potentially loss of money if you know how to use it rather than calling a Gas Safe registered heating engineer!
Types of Boiler Filling Loops
Boiler filling loops come in different types, each designed to suit specific needs and boiler configurations. The type of filling loop you use will depend on your boiler model and the setup of your central heating system. Here, we will explore the two main types of boiler filling loops: external and internal.
External Filling Loop
An external filling loop is installed outside the boiler and is used to connect the mains water supply to your central heating system.
Often referred to as a central heating filling loop, this type of filling loop features two control valves. One valve regulates the flow of water into the system, while the other affects the main lines.
External filling loops are straightforward to use and are typically found in older boiler models. They offer the advantage of easy access, making it simple to repressurise your boiler when needed.
However, it’s important to ensure that the filling loop is disconnected when not in use to comply with water regulations and prevent potential backflow issues.
Internal Filling Loop
An internal filling loop is integrated within the boiler itself, commonly found in modern combi boilers. This type of filling loop has one valve connected to the boiler and another connected to the mains water supply.
The valve attached to the boiler controls the water flow through the hose, while the valve connected to the mains water supply prevents water from flowing back into the mains.
A key feature of internal filling loops is the double check valve, which ensures that water does not backflow into the mains supply, maintaining the safety and integrity of your water system.
Internal filling loops are convenient and reduce the risk of accidental disconnection, making them a popular choice for contemporary heating systems.
By understanding the different types of boiler filling loops and their specific functions, you can better manage your central heating system’s pressure and ensure its optimal performance.
What is the purpose of repressurising my boiler & central heating system?
You may need to repressurise the boiler with an external filling loop for a variety of reasons, issues with central heating systems:
- The boiler pressure has fallen below 1 bar
- Your radiators have been bled
- There’s a tiny leak
- The boiler is having a problem
It is important to learn as much information as possible about the Boiler Filling loop. If you check the pressure gauge, your boiler’s pressure will be at an acceptable level (around 1.5 bar).
However, if this is different or not displaying the proper information, it could cause permanent damage.
It’s even more frustrating when low boiler pressure can be solved by a quick glance at the pressure gauge and repressurising system.
You can use external filling loops to connect to your mains water supply. This is necessary if your boiler or central heating water supply needs to be topped up.
How do you use a boiler filling loop?
Even if you aren’t sure how central heating and boilers work, using a boiler filling loop is an easy task. Some boilers have internal filling loops now, including the combi boiler filling loop, which is typically found in modern combi boilers. These tend to be on the more modern and better boilers.
If your boiler pressure drops too low, you will need one. Your boiler’s performance will be affected if it drops below half a bar. Your filling loop might be attached with blanking caps if it has just been installed.
To repressurise your boiler you won’t need any other tools. You can simply turn the filling valves with your hands. Before you begin, however, make sure the valves are in the “off” position.
- Use your hands to ensure that the filling loop stays in place.
- One valve should be turned so it aligns with the pipe’s direction
- Slowly turn the other filling valve. The water will begin to flow through the mains into your system.
- The system should allow water to flow through it. Your boiler’s pressure should begin to rise as a result.
- When it reaches 1.4 bar, shut down both valves.
Some people prefer to have the filling loop attached to the boiler. This is against the boiler filling loop regulations. They state that your filling loop must be disconnected from your boiler if it’s not being used.
It can cause irreparable damage and even death to your boiler’s filling loop. It can also be dangerous for children living in the home.
Children can knock out the filling loop valves. This could cause water to back up into the system. It would also raise the boiler pressure, which could lead to more problems.
Read our quick guide on how to repressurise a Worcester boiler here
Why are there filling loops that are not connected to the boiler at all times?
This is a simple one. Because water regulations prohibit water from returning to the mains, the connection between the boiler and filling loop is temporary.
You can’t use the same water from your radiators as the water coming out of the taps and showers. This is a very dangerous thought.
If you find yourself using the boiler filling loop for repressurising frequently, it could be an indication that there is a problem in your boiler or heating system.
The engineer should make sure that the boiler filling loop is accessible to you when the boiler is being installed. Boiler filling loops can be replaced if this is not the case.
A quick Google search will reveal that most online shops and services charge between £7 to £20 for a filling loop. This component is essential for repressurising your boiler. It’s worth having on hand!
The boiler’s filling line will contain at least one stop valve to regulate the flow of water, and understanding the placement of the filling loop valve is crucial for proper operation. A double check valve helps prevent water from returning to the mains.
What is the purpose of my filling loop and why do I need it?
The filling loop is designed to help you repressurise your boiler when the pressure drops too low and this is not something you should do all the time.
If you feel that your boiler is being topped up too often, usually more than twice per year, then there might be leaks.
You could have problems with pipes, radiators or other heating systems like expansion vessels and pressure release valves.
No matter what the reason, your boiler should not be low in pressure all the time. It is important to locate the leak quickly so that your boiler doesn’t suffer further damage.
You will see further corrosion if you need to refill your boiler frequently. The corrosion eventually leads to a buildup of sludge in your pipes and radiators.
This will cause your boiler to fail to heat up properly and will also lead to corrosion and component degradation that will create more problems.
If you find yourself using the boiler filling loop to pressurise frequently, it might be worth talking to heating specialists to get some reliable, friendly advice.
