I did a house today, and was sure it had Poly piping, but it was built in 1971. It looks like Poly on the outlet from the water heater. The heater is not original, and was replaced in 2001.
Then I see red piping at the bathroom sink, and grey in the kitchen… the red pipe isn’t Poly - does it look like PEX? Of course, no one knows when any work was done…

The red pipe looks like it might be PEX with a copper stub-out. Though the shade of red is different from most of the PEX I see.

That is what I think also. The grey pipe I do not know. If in doubt there is no shame in recommending a review by a local plumber.

I’m pretty sure the grey is Poly, but not sure how it got there. It looks like original work, but poly wasn’t available in 1971 as far as I know. I guess it could have been a remodel back in the 70’s or 80’s…

That is Polybutylene.

Looks like poly-B joined with a compression fitting to what looks like CPVC at the hot water tank. Probably from a reno done in the 80’s. Then pex under the sink from another reno later than mid 90’s. Or somebody had some old materials saved up from an earlier job, that happens too.
I just tell them what they got, and don’t try too hard to guess when they got it.

John Kogel

Definite poly. I would recommend that it be replaced.