If you go to a headshop, you normally just call them "pieces" unless you want to specify "water pipe" or just "pipe" to be safe. Bong has always had a marijuana related connotation to it, and most places will kick you out for calling it that. (By most I mean like 99.99%, the .01% being the one you are describing). They just don't want to get caught up with the legality issues.