Ok I got a little "tinkerish" last night and today and have taken these pictures, hopefully they come out well.
First is the clearo taken apart, and as you can see, it truly is a flat washer. This was the first one I experienced problems with and with Worksforme's suggestion, I screwed in the tip and just pulled - it came apart quite easily.
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Next is a picture of the underside of the chrome cap, and you can see the flat lip which is directly under the screw threads for the tip.
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Next picture is the washer placed back into place, not completely pushed down yet as you have to work it around.
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And finally a picture of the cap placed back on the clearo, and as you can see the lip of the clearo tank and the lip of the cap should hold the washer in place.
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Now...after doing all that and snapping the cap tightly over the clearo, the moment I put the tip back in, the washer came out again.
The cap came off this clearo very easily, but the other one, no amount of pulling and wiggling would release the cap from the plastic tank, even had hubby try it and it was a no-go.
The washer provides a seal to the tip, along with the little o-ring which is on the tip itself. In conclusion, I have found that the clearo works even without this seal, it has become more an annoyance than anything, for me at least. I placed the tip back into the other clearo without this seal, and just tightened it a little more and have had no other leaking issues.
Just wanted to post so that everyone would have a point of reference for that silly little rubbery thing that you could find floating in your clearo one day....