Well all of that might seem a mouthful, but it what it means is that our hot water will be ‘blasted’ out of the taps without the need for a pump! Mains pressure means the hot water comes out of the pipes at the same pressure as the cold water. Unvented means there is no cold water header tanks in the loft waiting to fill up with all sorts of nasties from your loft.
We went for a Range Tribune HE 210litre cylinder and it really looks the business!!! 
Always important for us that quality of design and feature is also matched by it looking good!
