IIRC, bongs are much more effective with vaporizers.
Since the cannabis does not go thru combustion, you are left with a lighter vapor in which the THC does not get trapped in the water. I'm not 100% sure though.

I've been using a bong with my vape for a few months now and the water stays clear and hardly even turned amber like it does when smoking.
I'm sure that it's still effective, because I've been using a lot less herb (cut my amount used by almost half).
I have my knob dialed in at around the 11 o'clock position which is still hot enough to burn my throat. That's why I like to use the water to cool the vapors.