starway6 wrote:I have to use some water because my bowl is plastic and the heat might melt it with out water to cool the vapor...
Air (and smoke) has very little heat capacity. Unless you are smoking literally non-stop for minutes, you are not likely to damage the bowl. The biggest risk is the brass stem overheating and deforming the hole in the plastic bottle it is fitted into.
Anyway, the water in a bong is not only there to cool the vapor, it is also there to absorb combustion gases like HCl and HCN that result from smouldering plant matter and act as irritants to the airways. If a lot of acidic gas dissolves in the water in your bong, then this would acidify the water and could cause the dmt freebase vapor to be salted and dissolved in the water.
As 1ce writes, some of the freebase dmt could be also simply be condensing onto the water.
If you are not burning enhanced leaf or changa in your bong, but only vaporizing freebase, there should be no acrid combustion gases if you vape correctly. In that case I would discard the water altogether and adopt a different smoking technique if the vapors are too hot for you to inhale directly. You could fill your mouth with vapor and then take your lips off the bong and at once inhale the vapor in your mouth together with as much fresh air as you can pull in along with the vapor. That'll also help to get the vapor deep into your lungs and help absorbtion.