Home made tank drier. Issue is copper / brass can scrape into tank threads / create a stress crack on inside / bottom surface. According to Faber, Asahi,...this is a serious issue. And is stricktly forbidden. DOT / NHTSB also warn of this. Same issue back when that company made SS tanks and they came into contact with multiiple iron fittings, etc. The mere touch of iron on the tank left a area of corrosion that hard buffing couldn't remove and the tanks evertually failed in the affected area.