Just had the house re-plumbed with PEX because of acidic water erosion. The
plumbers cut off and left the old copper pipe stubs protruding about an inch
from the drywall behind toilets and sinks. A much larger hole would have to
be made in the drywall in order to amputate these with a mini tube cutter
behind the drywall prior to patching the drywall. Internal pipe cutters
that I've seen are too large for 1/2 inch copper. Google search didn't turn
up anything readily.

Is there a better way ? Surely I'm not the first to encounter this problem.

David Merrill