The only way THC can be filtered out in water is by being attached to the tars, since it isn't water-soluble.
http://www.maps.org/news-letters/v05n1/05119wps.html

Due to stems/seeds/leaves having a higher tar content than buds do, it's possible that the studies that have shown that water filters out more THC than tars is because those were used instead/in combination with the buds. This is only a guess, but if that's true then smoking cannabis correctly (buds only) would most likely prove the opposite, and is probably the reason why water pipes are shown to be effective. Regardless, I get fucking blazed off of bongs... much moreso than pipes, meaning I will continue using water filtration as much as possible.
IllusionalFate Reviewed by IllusionalFate on . a nice glass pipe?? hey people..i just started smoking a couple of months ago...iv always rolled mine up but when my cousin came down to my house for a few days we smoked out of his bowl...the feeling for me was much better...i got high quicker and it was great...we were smoking non stop...iv been looking for a nice bowl and im excited about getting one...he got his from bigmikesglasspipes.com....i want to get one...which would look the best after being smoked out of?? Would my green fall through the hole if I get Rating: 5