whats people feelings on leaving deadlegs,,i have a situation were the gas pipe line needs upgraded from 15mm to 22mm,from the meter the pipe goes down and feeds the cooker and boiler in 15mm, the boiler pipe work comes up from a concrete floor,i can't access the pipe work as the floorboard section has these patterned sheets that inter lock,i could leave the 15mm gas pipework in and cap it were it comes up from the concrete floor but this leaves a 3 meter dead leg...thoughts please.