Mark Hansen wrote:
I thought this allowed rain water to drain as well. Otherwise, couldn't
the water build up and eventually get into the pressure line to the
ASI?

If there is a hole, then yes, it will drain water as well, because
there is flow into the tube. But without a drain hole, there is no air
flow into the pitot tube at all - so how will the rain drops get in? I
suppose if you flew through a heavy enough rain it could happen - but
that implies flying the plane IFR, and it's pretty rare for a plane to
be IFR capable and have no pitot heat. Rare, but not unknown.

Michael