Is on the wagon - Idioms by The Free Dictionary
be on the wagon (redirected from is on the wagon)
be on the wagon
To maintain one's sobriety; to abstain from alcohol. Jim's on the wagon again, so he doesn't want to go to the bar with us tonight.
be/go on the ˈwagon (informal) no longer drink/decide to stop drinking alcohol, either for a short period of time or permanently, especially if you drink a lot: ‘Would you like a gin and tonic?’ ‘No thanks. I’m on the wagon.’This idiom refers to the water wagon, which in America sprayed roads with water to prevent clouds of dust. If somebody starts drinking alcohol again, they are said to fall off the wagon.