Combination Boilers

A Combination boiler or also known as a ‘Combi’ boiler is an increasingly popular choice of boiler for homes across the UK. The reason for this comes down to a few different factors. A combi boiler requires fewer components to complete the system compared to that of a Regular or System boiler set-up. In a Combi system you don’t require a hot water cylinder, water storage cistern or expansion cistern, this is because the boiler heats your hot water almost instantaneously as and when you demand hot water. This is extremely efficient as no energy is wasted keeping it hot in a storage tank. The three main features of a combi boiler are to provide highly efficient hot water and central heating for your home and also to take up less space in your home, half of all the new boilers installed in domestic homes are combi boilers because of the simplicity and ease of installation.


  • Can be an economical option, as combi boilers only heat the water you use.
  • A great space-saving solution with no need for a separate cold water tank or hot water cylinder.
  • Installation may be quicker as there are fewer parts in a combi central heating system
  • Ideal for smaller houses and apartments.
  • Water is heated instantaneously when the hot water taps are switched on.



  • Depending on your mains water pressure, the flow of hot water could be reduced if you’re using more than one tap at the same time.
  • Water can sometimes take a few seconds to heat up
  • An electric immersion heater cannot be installed as a back up

Thermostatic Radiator Valves (TRV's)



A TRV senses the air temperature in the room and can be set higher in the rooms you use most and lower in rooms used less often such as bedrooms. They usually have a large valve at one end, typically marked from 0 to 6. Turning the dial up when the radiator is already on will not increase the room temperature! They can be used to turn an individual radiator on or off. At least one radiator should be left without a TRV and left permanently switched on, this radiator may be a bathroom towel rail (where the heat is always likely to be useful), or in the same room as the room thermostat where a TRV is not needed.

Combi Boiler Layout

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