new diy smoker

[beneficial7]

hi. have been building a smoker, 22.5" round, 36" tall. every piece has been hand crafted except for cooking grates, therm etc.... i work at an mechanical plumbing outfit, where i have access to various size ball valves. any recommendations on what size would be adequate for my intake. i am also fabbing up the damper for my flat lid, which could be any size as i have not started it yet.

                                                          thanks