Quote Originally Posted by BobBong
It's caused by a calcium buildup from the water..isn't it? The harder the water, the more calcium there is.

It's a hard water stain.

My bong has it
Thats what i always thought...

But the guy at my headshop suggested that i was using a weak salt (Morton's Salt) and it was reacting with the alcohol leaving the white residue.

Either way it sucks... i think im gonna put Draino or someother mineral solvent and just rinse it out real good...

I usually wash it out with antibacterial foaming dish soap after cleaning it anyways.