I dont mean to nit-pick but why-tf is everyone suggesting brass as a bong stem? It tarnishes (not just resinates) in water doesnt it? Also the pipes that are made of aluminum or brass are coated with a protectiv3 layer (aka "annodized") and this layer can be easily scraped off. Brass is not a metal it is an alloy which contains unknown quantities of LEAD and COPPER!!!!! Like they said, no (vomit alert) fucking stupid rediculous materials like rubber tubes, pvc, tinfoil boils and fucking tincans X(.

be safe, look for older steel sockets that dont have the shiny chromium coating because that shit cant be safe either. Dont use materials that rust in a bong. NO FUCKING GLUES, face it aside from using the stuff they sell in stores as a bench mark, I (and perhaps you) know very little about smoker safety (irony?). Dont scrape shitty metal pipes or stems and if you're truely worried about excess carcinogenic material in your smoke, why not drop a dime or two on a vaporizer or hot-air gun (aka desoldering gun) so you're not always breathing a mixture of burning plant and butane exhaust.

buy glass and keep smoking into older age

vaya con suerte