My neighbour owns a jewellry shop, and he owns a flat above it as well, with the bathroom directly over his workshop.His toilet has no overflow.It is a close coupled syphonic lever type.The distance from the toilet to the outside wall is ~4ft and the wall is mostly stone and plastered over.Is there any other way I can install an overflow pipe eg:I was thinking of cutting a hole in the WC pan connector and installing it into it with silicone but Im afraid of foul smells travelling up the pipe? Any suggestions appreciated.