Does anyone know what this blue thing is called?

[The Lamp Caretaker]

Does anyone know what the blue thing in this photo is called? I own one of the 5' water bubble lamps by Homedics and noticed this blue thing was flopping around in the box when I unpacked it the second time to run the lamp.  I could not figure out why it was in the box and had never noticed it before since the last time I ran the lamp several years ago.  This go-round when I plugged the lamp in no bubbles came out unless I squeezed one of the connecting tubes a few times. I happened to be online looking up the lamp on Ebay when I came across this photo if the interior of the lamp. I snipped a portion of the photo so everyone can see what I'm talking about.  Had it not been for this photo I would have never known why the blue thing was in the box.  The lamp worked fine before until I packed it away for several years. I'm assuming that the previous owner had issues with the blue thing and decided to replace it with the current clear type thing currently in it's place. The previous owner may not have been able to locate the original part and decided to leave the blue thing in the box for reference in case I was able to find the original part. 

[andy ross]

over here in uk it's called a "straight joiner" I think

[Claude J]

Just like an aquarium airline.
it is a check valve

[The Lamp Caretaker]

Thanks Claude - you hit it on the nail.  I'd misplaced the one that was in the box and wanted to replace it. I knew it was in the box -  just forgot where I placed it. So relieved. Yesterday as I was cleaning up I moved a rare mineral specimen that was sitting on my entry way table and there it was underneath where I'd placed it as I was setting up the lamp. Too bad I already took the lamp down so I was unable to test it now knowing how it works.  Air goes in one way not allowing water to back flow.  I looked up check valve and there it is exactly like the one that came with the lamp.  Explanation and all.  Thanks a ton.  I have no idea why it was replaced. I'm thinking of taking the lamp to my office and setting it up since it's a very cool lamp and would add some nice ambiance to the room.  Before I do I want to now buy a new one in case the one that came with the lamp is bad and the reason it was not on the lamp when I fired it up.  Hat's off to Claude!

[Claude J]

You are welcome
Glad to be of assistance
I had a grande fish tank at one time and replaced mine with one from Petco, it was only a few dollars at the time
Also, had a check valve on a column fish lamp I sold to a member.
They are there to protect the pump when shutoff so the water doesn't backflow into the diaphragm of the pump