Unvented & Megaflow Boilers

Learn more about the different types of boilers that are available to you.

What is an Unvented Cylinder (often referred to as a Megaflow System)?

This type of system accommodates almost all needs as it gives hot water to several taps at any one time at high pressure.

This type of system is suitable for all applications as it has all the benefits of both a conventional and combi system. So long as the incoming mains water pressure and pressure is high enough this system offers solutions to almost all possible scenarios, provided it is within your budget! It is essential before choosing this type of system that your installer checks both the incoming flowrate (normally a minimum of 18-22 litres per minute is best) and critically, the incoming mains pressure (recommended a minimum of 3 bar pressure).

So long as the above criteria are met, this system offers solutions to almost all possible scenarios, provided it is within your budget!


  • It eliminates the need for cold water storage tanks in the loft area (a good option if you are considering converting your loft space into living space). 
  • It also gives a very high pressure shower without the need for a mechanical pump. This saves on the cost of a shower pump and eliminates the noise element involved with mechanical pumps.
  • This type of system normally serves multiple taps simultaneously provided your installer has checked and confirmed the incoming mains flow rate and pressure are adequate.


  • Whilst it will tick almost every box in terms of hot water demand and flow rate, It is likely to be the most expensive option.
  • You must have your mains water pressure and flow rate tested before installation to ensure a minimum working pressure (any installer should carry out this test).

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