There has been studies with normal bongs and they mention some of the THC gets left behind in the water. With vaping it would seem you would loose a lot of cannabinoids because you are not heating the material up as much and a little water cooling effect could reduce huge amounts of your active...
I was wondering if this would be good to use to vape out of your bong or pipe? Seems rather inexpensive.
http://cgi.ebay.com/Ceramic-heating-element-heater-science-lab-vapor-200W_W0QQitemZ370454632272QQcategoryZ26261QQcmdZViewItem