should a check valve be a valve or a pipe?

[jamesuber]

Right now it seems to be considered to be a valve, different from a pipe. Result is that when you change a pipe to a check valve, then it gets confusing about whether that's really a different type of object, and existing data connections can be severed. For example a valve can accept a setting, but that doesn't apply logically to a check valve, so its more like a pipe in that case. however it's useful to keep track of check valves, different from pipes. So no change should be made to harm our ability to do that.