I just put these on my brew pots and all I can say is wow! They are truly massive, and they don't leak. If you're considering adding a valve to your brew pot using a weld less bulkhead I highly recommend using theirs. It is expensive, but it is also HUGE and 100% stainless steel.
http://www.brewershardware.com/Weldless-Bulkhead-1-2-MPT-X-1-2-FPT.html
Check it out
http://www.brewershardware.com/Weldless-Bulkhead-1-2-MPT-X-1-2-FPT.html
Check it out