I am trying to make a simple homemade percolator bong out of two water bottles, I know how to make it all, but I cannot get the two bottles to come together air tight, I went out and bought smart water bottles to because they are completely flat, but when I put the water in, it leaks out. I have tried just duct tape, but that obviously sucks, and I have tried hot glue and that melts the plastic a little and still isn't perfect, I didn't know if there were any tips or tricks I was missing.
Hot glue usually works for me. I've even fixed cracked bongs with those and its chill. Another ghetto method is to put gum over the gap/hole.
At my local hardware store they have this super glue that bonds instantly and gets super hot within seconds. Works pretty well.