I'm restoring a waters 600 + 410 + 996 that was used with THF and got stored with it for years.

I have noted some residues on the tubing, which i think it may be THF polymerization (little white spots on top left thick tube and central narrow tube in the photo).

My questions are: does anybody knows how to wash this polymer if possible?
Else, I'll have to replace some tubing on the gradient proportional valve and the output to the manifold, and in this case, the unions circled in red on the picture, are they just press fit with tubing of different diameters, or they come glued or ultrasound welded? Can i just pull it and put in the new tube?

Image

(PS: if it is peroxide, it didnt "puff" testing with a lighter, yodo)