Best Glue for plastic fermenter

I currently ferment in a 15 gallon extract container and I want to put a valve (maybe two) on the bottom so I can quit siphoning and having to move 10 gallons of beer around my garage. I can't reach inside the container so I have to cut a hole and glue it from the outside. Has anyone done this? The container is HDPE and it'd be best to find a "food grade" or "non-toxic" glue. Anyone know of something that would work?

Take your choice

Try a local rest. supply store, doubt you'll find it in a hardware store.

You may also want to look into a plastic welder if you want to avoid the gluing, though it does take some practice to get it right w/o weakening the plastic.

edit: I just took a look at that materials site. Be careful because I don't believe all those glues listed are food safe or proper for that type of job (i.e. cyanoacrylates bond really well but are brittle and if you jar the assembly hard enough, it will crack off, certain types of epoxy may leach nasty stuff, etc.).