I Ike the inner tube idea but the local kids aren’t going to be

too keen on “loaning” me one....
The expanding waterproofing foam seems to hold up reasonably well but I only have a short (3 month) experience with it in SC.
The brand is ‘GreatStuff’ and it is one of their specialty products for gap filling and setting pond rocks. Color choice is black.
I did a test sample (A) where I just filled a 1” dia pvc pipe to make a 2” long plug. It stuck like it never wanted to leave...ever.
It expanded to fill the diameter very nicely. ( a little goes a long way). I flipped the pipe over after 30 minutes and filled it with water. Weeks on and it hasn’t leaked. I attempted to push out the sample (A) plug but it wasn’t budging.
So I did another test sample (B) where I sprayed silicone lube in and on the 1” dia pvc pipe, let it ‘dry’ for 10 minutes then filled the pipe like before to make a 2” long plug. Again waited 30 minutes then flipped the pipe over and filled it with water. Again no leaks. After a couple days I drained the water out and was able to neatly push out the 2” long plug intact.
The results of the sample (B) test gives me some level of confidence that I can seal something up and have it conform to shape while still being able to cleanly remove it when needed.
The sample (A) test is a kinda permanent approach of sorts as the foam adheres to a clean dry surface very well....at least within a limited timeframe that is.
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