The benefits :
Unvented cylinders can provide mains pressure hot and cold water to all outlets provided the incoming mains pressure is correct, therefore shower pumps and cold water storage tanks are no longer needed saving valuable space. Unlike the combi boiler, unvented cylinders can provide larger and longer lasting hot water demands to many outlets simultaneously. Other advantages are reduced noise due to the fact that there is no cold water tank to fill and a reduced risk of contamination.
To install unvented systems requires the installer to be specially certified.
Unvented systems require unvented safety controls and pipework, which in the event of a fault will discharge water to outside. Therefore a route for the pipework can be challenging dependant on the location of the cylinder.