Conventional combis can still be erratic with hot water flow there is no airing cupboard to air clothes so you have to use a drier or radiators so wait 3 days there is no back up water supply in a tank when the water goes off. Drains are pipes, which carry waste and surface water from one or more houses when one drain meets another, it becomes a sewer these are not the gullies or grids that can be found in the road to take water off the highway. Manage your account online now with.