Discover the differences between low pressure heat only boilers and combination boilers for your bathroom. Learn which system suits your heating and hot water needs.
Understanding boiler types for your bathroom project
Choosing the right boiler system is key when designing or upgrading your bathroom. The boiler affects your hot water availability, heating efficiency, and plumbing setup.
Two common boiler types often considered for bathroom projects are:
- Low Pressure Heat Only Boilers (also called traditional or regular boilers)
- Combination Boilers (Combi boilers)
Let’s explore the differences, benefits, and which one might be best suited for your bathroom.
What is a low pressure ‘Heat only’ boiler?
A low pressure heat only boiler works by heating water that’s stored in a separate hot water cylinder (usually in an airing cupboard) and circulates heating water through your radiators. It uses gravity-fed cold water tanks in the loft or attic to supply water.
Key features:
- Requires a cold water storage tank (gravity system)
- Hot water stored in a cylinder for use on demand
- Operates at low pressure, hence the name
- Typically used in older homes with existing plumbing systems
What is a Combination boiler?
A combination boiler heats water directly from the mains supply when you turn on a tap, eliminating the need for a hot water cylinder or cold water tank. It provides instant hot water and central heating from one compact unit.
Key features:
- No need for storage tanks or cylinders
- Heats water on demand directly from mains pressure
- Compact and space-saving design
- Popular in modern homes and renovations
Installation & Bathroom project implications
| Feature | Low Pressure Heat Only Boiler | Combination Boiler |
| Space Requirements | Needs loft space for cold water tank + airing cupboard for cylinder | Compact unit; ideal for small spaces |
| Hot Water Availability | Limited by size of hot water cylinder | Continuous hot water, limited by mains flow |
| Water Pressure | Low pressure, gravity-fed system | High pressure, mains-fed system |
| Installation Complexity | More complex due to tanks and pipework | Simpler installation, fewer components |
| Energy Efficiency | Can be less efficient due to heat loss in tanks | More energy-efficient, less heat loss |
| Maintenance | Tanks require inspection, risk of leaks | Lower maintenance, fewer components |
| Cost | Lower initial boiler cost, but higher installation cost | Higher boiler cost, but simpler installation |
Pros & cons of each boiler type
Low pressure ‘Heat only’ boiler
Pros:
- Compatible with older heating systems
- Works well with multiple bathrooms and high hot water demand
- Can be used with solar thermal systems or water softeners
Cons:
- Requires more space for tanks and cylinders
- Water pressure may be lower, affecting shower experience
- More complex plumbing and potential for heat loss
Combination boiler
Pros:
- Instant hot water, no waiting for tank to heat
- Saves space with no tanks or cylinders needed
- Easier and cheaper installation in new builds or renovations
- High water pressure for showers
Cons:
- Water flow rate may limit simultaneous hot water use in multiple bathrooms
- Not ideal for larger homes with high hot water demand
- More expensive upfront boiler unit cost
Which boiler is best for your bathroom project?
| Choose a Low Pressure Heat Only Boiler if: |
| You have an older home with existing gravity-fed system |
| You require hot water for multiple bathrooms or high demand |
| You have loft and airing cupboard space available |
| Choose a Combination boiler if: |
| You want a compact, modern boiler with instant hot water |
| You have limited space for tanks or cylinders |
| Your home has one bathroom or moderate hot water demand |
Final thoughts…
Both low pressure heat only boilers and combination boilers have advantages depending on your home’s layout, water demand, and space. When planning your bathroom project, factor in:
- Available space for tanks and cylinders
- Number of bathrooms and simultaneous hot water needs
- Water pressure requirements for showers and taps
- Budget for boiler and installation
Why not reach out to us to assess your property and get us to recommend the best boiler system for efficient, reliable hot water and heating. Contact JW McDonald Building Services with your project requirements here.