The machine can also be used for high pressure cleaning of driveway, footpaths and brick work. Brenda from wigston on 31st march 2014. Aces21: energy-saving urea process. Only homeowners need to consider boiler cover. It varies from property to property hatches should be at least 300x300mm and positioned within 1.5 metres of any joint in the flue system the number of hatches.