Gas boilers and pressurised cylinders
🔥 Understanding Gas Boilers and Pressurised Heating Systems
A Homeowner’s Guide by MyBuild Renewables & Plumbing Ltd
When it comes to reliable, efficient home heating, few systems perform as consistently as a modern gas boiler combined with a pressurised (sealed) central heating system. Whether you’re upgrading an older setup or maintaining your existing boiler, understanding how these systems work—and why proper installation matters—can help you save energy, improve comfort, and extend the life of your heating equipment.
đź’§ What Is a Pressurised Heating System?
A pressurised (sealed) system is designed to operate without a traditional feed-and-expansion tank in the loft. Instead, it uses a sealed circuit of water kept under a set pressure—usually between 1.0 and 1.5 bar—monitored by a pressure gauge on the boiler or system pipework.
Key components include:
Expansion Vessel – absorbs changes in water pressure as the system heats and cools.
Pressure Relief Valve (PRV) – a safety device that releases excess pressure.
Filling Loop – used to top up the system if pressure drops.
System Filter – helps prevent sludge and debris buildup.
This design makes the system quieter, more efficient, and less prone to airlocks or corrosion compared to older open-vented systems.
🔧 How the Gas Boiler Fits In
Your gas boiler is the powerhouse of the system. It heats water that circulates through radiators, underfloor heating, or a hot water cylinder. There are three main types of boilers:
Combi Boilers (Combination Boilers)
Provide both heating and hot water on demand.
Ideal for smaller homes or properties without a loft.
No need for a separate cylinder or tank.
System Boilers
Work with an unvented hot water cylinder.
Great for medium to large homes with multiple bathrooms.
Offer high hot water flow rates.
Regular (Heat Only) Boilers
Use a separate hot water cylinder and feed tanks.
Common in older properties or large homes with traditional setups.
At MyBuild Renewables & Plumbing Ltd, we install Gas Safe–registered boilers from trusted brands such as Ideal, Worcester Bosch, and Vaillant, offering free 2-year workmanship warranties on all installations.
⚙️ Advantages of a Pressurised System
✅ Better Performance – Higher, consistent water pressure for radiators and hot taps.
✅ Space Saving – No need for loft tanks or vent pipes.
✅ Improved Efficiency – Sealed systems reduce oxygen ingress, which minimises corrosion.
✅ Compatibility with Renewables – Pressurised systems pair perfectly with air source heat pumps, solar hot water, or hybrid systems.
✅ Low Maintenance – Modern designs are easier to maintain and monitor.
🧰 Maintenance & Safety Tips
To keep your system running safely and efficiently:
Check your pressure gauge regularly (should be around 1.2 bar when cold).
Bleed radiators if air builds up.
Book an annual Gas Safe service to ensure safe combustion and efficiency.
Install a system filter to trap magnetite and sludge.
Use inhibitor chemicals to protect against corrosion.
At MyBuild Renewables & Plumbing Ltd, we provide annual servicing, system flushes, safety checks, and full boiler replacements across Portishead, Bristol, and North Somerset.
