Broken steel 1/2 inch supply line. Need to replace section that is in a wall cavity.Can the steel pipe be cut and some sort of union or compression fitting be used to connect it to new copper piping without having to thread the existing steel pipe in wall?I do not see a way in wich you could thread the existing pipe in wall cavity due to clearance issues(very tight limited access). This supplyline runs up from basement through kitchen exterior wall to bath on second floor.pipe access is extremely limited.