Our current heat pump uses R22 and we'll be switching to R410a. As we all know, everyone seems to have a different opinion. I've been told that flushing the pipes will be fine and I've also been told that new pipes should be installed because oils can get into the new heat pump (that will use 410a) from the R22 and destroy the new heat pump. Is there any truth in this? Our pipes are in the walls so it will be rather difficult to pull them out and install brand new pipes. What is the truth on this issue?