System Boilers — Bournemouth, Poole & Dorset
A system boiler works alongside a hot water storage cylinder to deliver heating and hot water across larger homes and properties with multiple bathrooms. All the key components are built into the boiler unit itself, making installation cleaner and faster than a traditional heat only setup — while still offering the high hot water output that a combi cannot match.
Installations from £1,299 + VAT · Free Site Visit · Gas Safe Registered · 01202 668822
What Is a System Boiler?
A system boiler heats your central heating circuit directly and also heats a separate hot water storage cylinder. Unlike a heat only (regular) boiler, all the main components — expansion vessel, pump, and controls — are built into the boiler unit. As a result, there’s no need for a cold water tank or feed and expansion tank in the loft, which keeps the installation tidier and the loft free.
Hot water is stored in the cylinder and delivered at mains pressure, so you can run multiple showers or taps simultaneously without any drop in performance. This makes system boilers the preferred choice for larger homes and families across the Dorset area with higher hot water demand.
Like all modern boilers, system boilers are condensing units, typically achieving ErP A efficiency ratings of 90% or above — so despite the larger output, running costs remain competitive.
How Does a System Boiler Work?
Understanding how the system works helps you manage it effectively and spot any issues early.
The boiler heats water and stores it in an insulated cylinder, typically located in an airing cupboard. When you open a hot tap, pre-heated water flows from the cylinder at mains pressure. Because it’s stored and ready, hot water delivery is fast — and unlike a combi, there’s no limit on how many outlets can run at the same time, provided the cylinder has enough stored volume.
For heating, the boiler circulates water around your radiators via the built-in pump, returning cooled water to be reheated. The system operates independently from the hot water circuit, so heating and hot water can run simultaneously without any compromise in performance.
A system boiler operates as a sealed system — the built-in expansion vessel absorbs pressure changes as the water heats and cools, meaning no open-vented tank is required in the loft. This reduces the risk of contamination and keeps the system pressurised for optimal performance. You’ll need to top up the system pressure occasionally via the filling loop if it drops below the recommended level.
System Boiler Advantages & Limitations
A system boiler is the right solution for many homes in Bournemouth and Poole — but as with any boiler type, it comes with trade-offs worth understanding before you commit.
►High hot water output — multiple showers and taps can run simultaneously
►No loft tanks required — cleaner installation than a heat only system
►Mains pressure hot water — strong, consistent flow to all outlets
►Compatible with solar thermal — the cylinder can incorporate a solar coil
►Faster installation than heat only — all components built into the boiler
►Requires space for a hot water cylinder — typically an airing cupboard
►Higher installation cost than a combi — due to the additional cylinder
►Hot water is not truly instant — the cylinder must reheat after heavy use
Is a System Boiler Right for My Home?
A system boiler suits larger homes with three or more bedrooms, multiple bathrooms, or households with high simultaneous hot water demand. It’s also a good choice if you already have a hot water cylinder and want to upgrade the boiler without changing the wider system.
For smaller properties or those where space is limited, a combi boiler may be more appropriate. Call us on 01202 668822 and we’ll advise, or book a free site visit.
Why Choose Dorset Plumbing to Install Your System Boiler?
Gas Safe Registered ✓ — all engineers hold full Gas Safe registration (No. 943146).
All Major Brands ✓ — we install Worcester Bosch, Vaillant, Baxi, Ideal, Viessmann, Glow-Worm, and more.
Free Site Visit ✓ — before recommending a model or cylinder size, we assess your property and hot water demand at no charge.
Transparent Pricing ✓ — fixed written quotes with no hidden charges.
Finance Available ✓ — spread the cost over 2 to 5 years, no deposit on approved credit.
Locally Based in Poole ✓ — fast response across Bournemouth, Poole, and Dorset with no inflated travel charges.
System Boiler Installation Areas — Bournemouth, Poole & Dorset
We install system boilers across Bournemouth, Poole, Christchurch, and the surrounding Dorset area. Because we’re locally based in Poole, response times are fast with no inflated travel charges.
Bournemouth: Boscombe, Southbourne, Winton, Moordown, Charminster, Kinson, Westbourne, Talbot Woods, Pokesdown, Iford, Hengistbury Head
Poole: Sandbanks, Parkstone, Lilliput, Whitecliff, Canford Heath, Broadstone, Hamworthy, Oakdale, Creekmoor, Branksome
Wider Dorset: Christchurch, Highcliffe, Ringwood, Ferndown, Wimborne, Verwood, West Moors, Wareham, Blandford Forum
Not listed? Call us on 01202 668822 — we likely cover your area.
Frequently Asked Questions — System Boilers
Cylinder size depends on the number of bathrooms and the household’s hot water demand. As a general guide, a 150-litre cylinder suits a three-bedroom home, while a 210-litre or larger cylinder is more appropriate for four or more bedrooms. During our free site visit, we’ll recommend the right size for your property.
Both types use a hot water cylinder, but a system boiler has the pump, expansion vessel, and controls built in — so there’s no need for a separate feed and expansion tank in the loft. A heat only boiler requires those additional components to be installed separately, making the system boiler the simpler and tidier modern equivalent.
Yes. Switching from a combi to a system boiler involves installing a hot water cylinder and modifying the pipework accordingly. It’s a more involved job than a like-for-like replacement, but it’s a worthwhile upgrade for growing households where hot water demand has outgrown what the combi can deliver.
System boiler installations start from £1,299 + VAT, though the total cost will depend on the boiler model, cylinder size, and any pipework modifications required. We provide a fixed written quote after a free site visit — call us on 01202 668822 to arrange.