After 4 months of storage, my Keurig didn't operate correctly when I tried using it again. The "add water" blue light, the "heat" red light and the middle "coffee cup" blue light, all x3 lights, blinked together... and the unit was seized up it seamed when I would try using it. After pulling the bottom apart and checking all those tubes, I found this web page, and then put the bottom back together again, and removed the top part to get to the "water pump" [check valve actually], and blew into it; it was completely seized. I blew a short spurt really hard un-siezing it. That's all it took. It was stuck from being in storage, dried out and sealed as it dried out. I put everything back together and I had to run the unit a few times until everything worked as it should. I really enjoyed this thread and everyone's collaboration, as it solved the root of my problem, which I couldn't find resolution anywhere else. Thanks a bunch! Don't forget to click on and read the detailed comments people wrote for each step...

*before tugging upwards on the elbow tube, which is currently slid onto a black hard plastic tube, there is a compression ring made of similar clear tube material that should be slid up, so that the compression ring is NOT compressing that clear tube on to that black hard plastic tube. When the compression ring is slid up and not compressing anymore, it will be much easier to pull the elbow tube off (and put on) [I think I used x2 spoons to get down in there and evenly pull/slide the compression ring up. Note: I gently used a flat screw driver to put the "flat" at the very bottom edge of the clear tube to help slide it off and use the screwdriver like a teeter-todder which helped push the clear tube up, as I pulled the elbow tube off. -When ready to install, slide the clear tube back onto the black hard plastic tube all the way down, and THEN slide the compression ring down onto where both tubes are now overlapping, ensuring the clear tube is compressed by the compression ring onto the black plastic tube.