Unvented Hot Water Systems provide stored hot water at mains pressure. This provides a number of benefits over traditional vented hot water systems as they provide both hot and cold water at mains pressure this means they require no cold water storage cistern and therefore does not rely on the 'head' of pressure. This allows the use of power showers without the use of additional pumps. It also overcomes the the risk of pipes freezing in lofts. Unvented Systems can also offer more flexible installation solutions. Due to the potential hazards of incorrectly installed Unvented Hot Water Cisterns, like Gas only certified installers are allowed to install and sign them off.