We aim to fit premium quality products and primarily install Worcester Bosch and Valiant products for peace of mind, which all come with a guarantee, but can source all brands of boiler depending on requirements. In an unvented system there is no cold water tank - instead, the sealed hot water cylinder is fed directly by the cold water mains. Since they are operating at mains pressure, they offer much better flow rates, meaning your shower and bath performance should be higher. If you rent out a property, you're legally obliged to have a gas safety check carried out by a suitably qualified and registered Gas Safe engineer.