I've read that a bong traps more THC than tar so using water cooling for a vape is a waste of good herb. THC may not be water soluble but is it being cooled in the water so much that it condenses back into a resin in the water? I use a home made vape with a bong downtube and there's plenty of condensed resins on the glass - they taste really sweet and herby too if you fancy a taste:jointsmile: