Is your boiler system suffering from inefficiencies? Are there uneven heating spots throughout your property? Maybe heating doesn't properly reach higher floors? The core cause of all these issues is likely inadequate pressure in the boiler system, which causes slower circulation, impacts heating performance, and can overwork the system.
In this article, we'll teach you everything you need to know about boiler repressurisation, give you a step-by-step guide on refilling a central heating system with a combi boiler, and offer tips to help you maintain your system going forward.
What Does Refilling or Repressurising a Combi Boiler Mean?
Refilling or pressurising a boiler refers to the process of introducing additional water supply to a boiler system to increase the boiler pressure, usually to 1 or 1.5 bar.
Maintaining a boiler's pressure is critical to the overall function of the heating system and its subsystems. A boiler without adequate pressure can't circulate water effectively, leading to cold spots, ineffective heating, a hissing sound in the radiators, and a variety of other issues.
Why Does the Boiler Pressure Drop?
Boilers are closed systems, so theoretically, the pressure should remain constant; so how could the pressure drop? There are two primary causes:
- Leaks in the system: Most boiler systems have complex pipe networks, and any leaks in these systems can lead to a dwindling water supply and thus lower pressure in the system. Low pressure doesn't only result in low pressure, however, it can also introduce many other problems and cause long-term harm to your property.
- Air pockets in the radiators: With time, because radiators aren't perfectly airtight, pockets of air start developing, which impede the circulation of water and result in both lower pressure and other inefficiencies. This is solved through a process called radiator bleeding.
- Maintenance work: If you need to remove sludge, perform repairs, or otherwise make fundamental changes to the heating system, you likely need to drain the water from the system. But once the repairs are done, you need to properly repressurise the boiler again to ensure effective work.
- Core issues with the system: Modern boilers are equipped with a pressure release valve that automatically opens if the pressure in the system reaches critical levels, and this can happen for a variety of reasons. But due to releasing steam, this process necessarily lowers water levels and subsequently pressure in the system once the boiler is in normal working conditions again.
How To Know My Boiler Needs Repressurising?
Identifying when your system needs repressurisation promptly is critical to the continued operation of your boiler system. A boiler operating for multiple days or weeks in a low-pressure environment can cause permanent damage to the system and necessitate costly repairs. This is why we've compiled a list of signs you can use to identify when and why your system needs repressurising:
- Check the Pressure Gauge: The easiest way to tell if a heating system suffers from low pressure is by checking the pressure gauge. The boiler's pressure gauge should read between 1 and 1.5 bar. Lower pressure levels will impede the proper circulation of water in the system.
- Look for tell-tale signs of low pressure in the system: There are obvious signs that a system is suffering from low pressure. This includes uneven and spot heating, creaking sounds, and high energy consumption. If your boiler is exhibiting a combination of these signs, it is likely suffering from a low supply of fresh water.
- Leaks or other issues: If the system is suffering from leaks or is unoperational due to issues in the pipe network, this naturally results in lower pressure in the system. The repairs won't only involve fixing these issues, but they'll also require repressurising the boiler.
Step-by-Step Instructions on How to Refill Your Central Heating System
If this is your first time, refilling your combi boiler system might seem daunting, but there are a few core tasks you need to take care of. Once those are done, the process is relatively straightforward and routine.
Turn Off the Boiler
Naturally, the first step in repressurising the system is turning off the boiler and power supply. This is necessary to prevent any accidents during the refilling process.
Shutting Off the Bleed Valves and Drain Offs
If before refilling the system, you've drained it, it is very important you disconnect the hosepipe, shut off the air vents and the drainage valve. If you don't, you run the risk of water leaking from the system.
The bleed valve is usually located on the side of the radiators, but each system is different, and you should check the manual to confirm where the air vents of your combi boilers are located.
Identify the Filling Loop
The filling loop is a hose pipe that connects your boiler to the main hot water supply. Identifying it is key to repressurising the system. Most systems either have filling loops situated on the pipe network or an internal filling loop directly connected to the boiler. Each radiator also has an individual filling loop.
Start by opening the boiler's filling loop and work your way up the building, opening up the filling loops of the radiators from bottom to top.
Reconnecting the Boiler to the Mains Water Supply
After making sure there are no avenues for water to leak from the combi boiler, it is time to restart the water flow to the system. Make sure you monitor the boiler pressure during this stage. Once the pressure gauge reads between 1 and 1.5 bar, that means enough water has entered the system.
Bleed the Radiators
Your job isn't finished once the pressure gauge hits the 1 to 1.5 bar range, however. When a boiler system lacks proper levels of water, it leaves a vacuum, both literally and figuratively. Air pockets start to form in the radiators and pipes that impede the flow of water as the boiler system slowly starts to fill up.
Once you reach the desired pressure, it is time to bleed the radiators. You need the radiator key, a towel, and a container. The radiator key or the bleed key, is a tool that comes with every radiator and allows you to open the bleed valve. Start from the lowest radiator in the building and work your way up.
Once you open the valve, don't close it until you allow all the air escaping the radiator to go through, then close the valve and clean the area with a cloth. Repeat the same process for every radiator on the property.
Add Inhibitors to the System
Once you've introduced new water to your system, it is important you add inhibitors, which are chemicals that protect against rust, corrosion, and scaling in both the boiler and the pipe network.
The process is pretty straightforward. Purchase an inhibitor agent you trust, read its manual to find out the volume you need for circulation, and that's it. This should help you maintain the integrity of your boiler against corrosion and scaling, which are serious issues.
Turn On Your Combi Boiler
Once the filling loop has been opened, the drainage valve closed, and the low boiler pressure addressed, there's only one thing left: Turning on your boiler! Congrats, it should be in fully working order now!
Tips to Maintain Combi Boilers
Low boiler pressure isn't the only issue central heating systems regularly suffer from. Learning how to maintain them can be key to reducing repair needs and costs while increasing the system's longevity and durability. Here are some key tips to maintain your central heating system:
#1 Service Your Boiler Regularly
Prevention is better than a cure, which is certainly true for boiler maintenance. Servicing your boiler regularly, checking up on its pressure gauge, filling loop, and pipe network to ensure there are no technical issues or leaks, is key to maintaining your combi boiler in full working condition and avoiding costly repairs.
#2 A Robust Pipe Network Is Key to a Healthy Combi Boiler
If the combi boiler is the heart of your heating system, then the pipe network is its veins. If the pipe network is robust, properly insulated, and well routed, it not only maintains the boiler pressure but it will also reduce energy costs and system load. In other words, it'll make your system healthier, more affordable, and more efficient.
#3 Make Sure the Boiler Room is Well Maintained and Ventilated
High temperatures and humidity can impede the boiler operations, leading to inefficient heat transfer and degradation. This is why most boiler manufacturers highly recommend that boiler room temperatures do not exceed 40 degrees Celsius.
If you want to keep your boiler in a great shape, you can start by ensuring the boiler room is well maintained and properly ventilated.
#4 Be Aware of Your Property's Heating Needs
Being aware of your heating needs means that you can avoid overworking your combi boiler. If there are extended periods where your heating needs are minimal, you can turn off the boiler to maintain its health and reduce energy consumption.
#5 Be Aware of Signs of Trouble
Do you hear air escaping from your radiators? Are there signs of leaks in your house? You don't need to wait for the boiler pressure gauge to show red to act. Often, there are many signs that there are issues with the system. Being aware and on the lookout for these signs allows you to act quickly and perform critical repairs before they do lasting damage to your boiler.
Conclusion
Repressurising your combi boiler is a crucial part of its maintenance routine, and property owners must learn how to do the basics. Thankfully, it is largely a routine job that doesn't require any specialised knowledge and equipment and can be performed with ease by homeowners -- if they know what they are doing. This is where this guide comes in, giving you everything you need to know to repressurise your system.
If the process still seems daunting to you, you can get in touch with a Gas Safe registered engineer to handle the repairs for you.