I'm not particularly experienced with smoking/vaporizing or using Methamphetamine in general, but I understand that a lot of people use Meth with a water filtration system.
When you say "attachment" assuming you mean a bulb-type thing that is commonly used to vaporize Meth?
I think it's fine. Just like when using a bong to smoke Cannabis, there will be a certain, probably small amount of the drug lost in the water. We were recently discussing this in another thread. Slightly off topic, but you can probably reclaim any drug filtered out simply by letting it evaporate and collecting the re-crystallized drug.