Openreach guy came round today and was pretty helpful. He wasn't too happy that I want to bring the ducting under the B&B floor and into the under stair cupboard. His issue is any gas or water coming through the duct into the house. He said they normally use a resin on an outside pipe but we have radon gas and I would therefor need a duct cap that can seal any gases. Has anyone come across this issue?   Cheers   Vijay