The plastic tubing supplying filtered water to our refrigerator currently runs below a suspended ceiling. I want to reroute it above. How do I disconnect it without damage from either the union or tee, so I can reconnect once moved? The tee is labeled NSF-51 Parker Parflex size 4. The union has no discernible markings. I believe I would rather disconnect the union rather than the tee. I didn't want to just start tugging. I have found similar fittings for sale online, but no instructions for use.
Here is the union:
And here is the tee: 
Best Answer
Just to add some visuals to the others' explanations using your photo, you need to (1) push on the collar trying to move it parallel to the tube, and (2) pull the tube.
To reconnect, push the tube into the collar until it stops (should be about 1 inch). Make sure the tube end is square (perpendicular to the tube axis, with no damage); cut a bit of the tube if necessary.