it will work but you have to drink it all man. CHUG IT!! as has been mentioned before, thc has very low solubility in room temperature water, but there is still some so if you've used the water for a long time there can be enough in there to get you pretty fucked up. boiling it will cause the water to steam off and leave all the good stuff like THC
seriously tho......hookah/bong water is mostly tar and harmful chemicals.....almost no THC...toss that shit down the drain