We need to move our washing machine from the kitchen to the garage,however to run the waste water to a drain means a very long run alon the side of the house with a very shallow fall on it.Another option is to connect to a downpipe which is on the side of the garage this takes rainwater off the entire large roof and the extension roof.So my question is this,surely this must connect to a drain and not a soakaway to cope with the volume of water in heavy rain.So can I connect to it and how could I check that it is not a soakaway?