Types of Boilers Explained | Tonbridge Plumber Guide 2026
When your boiler needs replacing, choosing the right type matters as much as choosing the right brand. The boiler that works perfectly for a compact flat in Tonbridge town centre may be entirely wrong for a large family home in Hildenborough or a period property in Shipbourne. Understanding the different boiler types helps you make an informed decision that suits your home, your family’s hot water demands, and your budget.
This guide explains the three main boiler types available to Tonbridge homeowners—combi boilers, system boilers, and conventional boilers—covering how each works, their advantages and disadvantages, and which properties they suit best.
How Boilers Work: The Basics
Before comparing boiler types, it helps to understand what all boilers do. Every boiler heats water using gas, oil, or electricity. That heated water then either flows directly to your taps and showers (hot water) or circulates through radiators (central heating).
The differences between boiler types come down to how they store and deliver hot water, whether they need additional tanks and cylinders, and how they manage demand from multiple outlets simultaneously.
Combi Boilers
Combi boilers—short for combination boilers—are the most popular choice in UK homes, accounting for over half of all new installations. They provide both central heating and instant hot water from a single compact unit, with no need for separate tanks or cylinders.
How Combi Boilers Work
When you turn on a hot tap, the combi boiler fires up and heats water directly from the mains as it passes through the unit. There’s no stored hot water—the boiler heats it on demand, delivering it straight to your tap or shower. When you turn the tap off, the boiler stops heating.
For central heating, the boiler heats water that circulates through your radiators in a sealed system. The same boiler handles both functions but not simultaneously—hot water takes priority over heating when you open a tap.
Advantages of Combi Boilers
Compact size: With no need for tanks in the loft or cylinders in airing cupboards, combi boilers free up valuable storage space. The boiler itself is typically wall-mounted in the kitchen, utility room, or garage.
Instant hot water: Hot water is available on demand without waiting for a cylinder to heat up. No more timing your showers around the immersion heater.
Energy efficient: You only heat water when you need it, avoiding the energy losses associated with storing hot water in a cylinder.
Lower installation costs: Without tanks and cylinders to install, fitting a combi boiler is typically simpler and cheaper than other systems.
Mains pressure delivery: Hot water comes at mains pressure, meaning powerful showers without needing a pump—assuming your mains pressure is adequate.
Disadvantages of Combi Boilers
Limited flow rate: Combi boilers can only heat a certain amount of water per minute. Running multiple hot water outlets simultaneously—two showers at once, or a shower and a kitchen tap—may result in reduced flow or temperature fluctuations.
Dependent on mains pressure: If your mains water pressure is poor, your hot water pressure will be too. Some older properties in Tonbridge may experience lower mains pressure than newer developments.
No immersion backup: If your combi boiler breaks down, you have no hot water at all. Cylinder-based systems can use an immersion heater as backup.
Who Should Choose a Combi Boiler?
Combi boilers suit small to medium-sized homes with one bathroom or one bathroom plus en-suite. They work well for households with moderate hot water demand and properties where space is limited.
Many properties across Tonbridge—including flats and terraces near the High Street, semis in Higham Wood, and family homes in Cage Green—suit combi boilers perfectly. They’re particularly popular in newer properties and homes where maximising storage space matters.
System Boilers
System boilers work with a hot water cylinder but don’t require cold water tanks in the loft. They’re sometimes called sealed system boilers because they operate on a sealed heating circuit fed directly from the mains.
How System Boilers Work
The boiler heats water that’s stored in a hot water cylinder, typically located in an airing cupboard. When you open a hot tap, water flows from this cylinder rather than being heated instantaneously. The cylinder refills and reheats automatically.
For central heating, the same boiler heats water circulating through radiators in a sealed system—similar to a combi boiler.
Advantages of System Boilers
Better for multiple outlets: Because hot water is stored in a cylinder, you can run several taps or showers simultaneously without losing pressure or temperature. The cylinder delivers stored water while gradually refilling.
Compatible with high-flow showers: System boilers work well with powerful showers and multiple bathroom setups. Large families benefit from the stored hot water capacity.
Mains pressure throughout: Like combi boilers, system boilers operate at mains pressure, delivering good water pressure to showers and taps.
No loft tanks: Unlike conventional boilers, system boilers don’t need cold water tanks in the loft, reducing frost risk and freeing up loft space.
Immersion backup: Most cylinders include an immersion heater element, providing emergency hot water if the boiler fails.
Disadvantages of System Boilers
Cylinder space required: You’ll need an airing cupboard or utility area for the hot water cylinder. This isn’t always available in smaller properties.
Hot water can run out: If your household uses more hot water than the cylinder holds, you’ll need to wait for it to reheat. Correct cylinder sizing is important.
Higher installation costs: Installing a cylinder alongside the boiler adds cost and complexity compared to a combi-only installation.
Who Should Choose a System Boiler?
System boilers suit medium to large homes with multiple bathrooms and households with high simultaneous hot water demand. Families who regularly run multiple showers at once benefit from stored hot water capacity.
Larger family homes across Tonbridge—particularly detached properties in Hildenborough, larger semis in Hadlow, and period homes in Shipbourne with multiple bathrooms—often benefit from system boilers.
Conventional Boilers
Conventional boilers—also called regular boilers, traditional boilers, or heat-only boilers—are the oldest boiler type still in common use. They work with both a hot water cylinder and cold water tanks in the loft.
How Conventional Boilers Work
Cold water is stored in a tank in your loft (the cold water storage cistern). This feeds a hot water cylinder, where the boiler heats it. When you open a hot tap, gravity feeds hot water from the cylinder to your taps.
A separate small tank in the loft (the feed and expansion tank) maintains the central heating system, which operates at low pressure.
Advantages of Conventional Boilers
High hot water capacity: Large cylinders can store substantial amounts of hot water, suitable for households with very high demand.
Compatible with older systems: Conventional boilers work with existing pipework in older properties designed for this setup. Changing to a combi or system boiler may require significant pipework modifications.
Good for areas with low mains pressure: Because the system uses gravity from loft tanks, low mains pressure doesn’t directly affect hot water delivery.
Power shower compatible: The low-pressure system works with power showers that have their own pumps.
Disadvantages of Conventional Boilers
Space requirements: You need loft space for two tanks plus airing cupboard space for the cylinder. This uses significant storage areas.
Lower pressure without pumps: Gravity-fed systems deliver lower water pressure than mains-pressure alternatives. Many homeowners add pumps to improve shower performance.
Frost risk: Tanks in the loft can freeze in severe weather if not properly insulated and protected.
Less efficient: The combination of stored hot water and tank heat losses makes conventional systems typically less efficient than modern alternatives.
Who Should Choose a Conventional Boiler?
Conventional boilers suit properties already fitted with conventional systems where changing would be disruptive, older homes with pipework designed for gravity-fed systems, and listed buildings where alterations are restricted.
Some period properties in Tonbridge—particularly Victorian and Edwardian homes around the town centre and older cottages in surrounding villages like Bidborough and Penshurst—may retain conventional systems where replacing like-for-like proves simpler than converting.
Choosing the Right Boiler for Your Tonbridge Home
Several factors influence which boiler type suits your property.
Property Size and Bathrooms
Count your bathrooms and consider typical usage patterns. One bathroom typically suits a combi boiler. Two or more bathrooms with family members showering simultaneously may require a system boiler’s stored capacity.
Mains Water Pressure
Check your mains pressure before deciding. If pressure is poor—more common in older parts of Tonbridge and some rural areas around Hadlow and Shipbourne—combi boilers may disappoint. Your plumber can test mains pressure during a survey.
Available Space
Do you have an airing cupboard for a cylinder? Loft space for tanks? If space is tight, a combi boiler’s compact footprint becomes attractive.
Current System
What do you have now? Converting from conventional to combi requires removing tanks and cylinders and modifying pipework—additional work and cost. Sometimes upgrading like-for-like is more practical and cost-effective.
Future Needs
Consider how your household might change. Children growing up means more showers. Extended family moving in means additional demand. Choose a boiler that handles future needs, not just current ones.
Getting Expert Advice
Every home is different, and the right boiler depends on your specific circumstances. A professional assessment considers your property’s characteristics, your household’s hot water demands, existing infrastructure, and budget constraints.
We install and replace boilers throughout Tonbridge and surrounding areas including Hildenborough, Hadlow, Shipbourne, Bidborough, Southborough, Pembury, Paddock Wood, East Peckham, and surrounding Kent villages. Our Gas Safe registered engineers assess your property, explain your options clearly, and recommend the boiler type that genuinely suits your needs.
Considering a new boiler for your Tonbridge home? Contact us for a free assessment and honest advice on which boiler type suits your property and family.