The following is a basic description of how to drain down and repressurise a combi boiler system layouts will vary, but basic components will be the same. Our technicians and installers are here to make sure that your a/c systems work efficiently, relaible and safely year round call us today for cooling services! Plumbing & heating in halifax, west yorkshire. Be entered into our monthly prize draw when you sign up for newsletters! Old, low-efficiency heating systems.