Fixture tailpieces should be at least _____ inches in diameter for sinks, dishwashers, laundry tubs and similar fixtures (IRC 2006).
What’s your guess? (try to refrain from copy/pasting)
1 1/4 bath sinks
1 1/2 other sinks
2" shower and tub
ditto james.
1 1/2" to answer the question as asked.