I am needing to do some plumbing repairs to a manufactured homes kitchen sink plumbing. The incoming plumbing is a white, small diameter, flexible tubing that looks like PEX, but elbow connections that branch from the lines look to be glued. Shut off valves are grey PB that attach to the white tubing via a threaded connection. The outlet from the valve is a compression fitting with more of the white flexible pipe. How can I identify this white tubing? Can I assume it is PEX or is there another type of tubing?