to the camper water system, and since it was too long,
I took a small sample piece to the local hardware store
to find out what it is. It turns out to be polybutylene, and
that stuff has been out of use for a long time, and no fittings
are even sold for it. However, rubber compression cones are
available that fit it, so I cut off about 6" of excess pipe and put
it back together. Working fine, so far.