Well i know that when you pull the bowl out the smoke is supposed to clear but i just made a water bottle gravity bong and it just dosnt work. Heres a pic of it, tell me if i did something wrong.
O then i guess i didnt know what i was doing lol. Well when you pull the trumpet mouth peice out i expected for the smoke to clear but it dosnt.
uh, then suck harder?? this is a gravity bong by the way: http://www.waytoomany.com/vids/weed/simple_gravity_bong.php
no, never use foil. you can probobly get a cheap slide on ebay and use that by drilling a hole big enough to fit it in the bottle cap. i hope im allowed to give ebay as advice, if not im sorry.
No, I mean like take the cap off the bottle, and replace with a foil wrap as cap/bowl. and you can take it off and put it back on for hits. My friend did that and it worked fine. But I personally use a metal bowl fit into a drilled hole of a cap.
I got a brass fitting and drilled/tapped the cap for 1/4" npt threads, it sealed perfectly and made a wicked gravity bong but I've never had the desire to do it again. Not a real chill smoking method..