water wagon

a wagon used to transport water, as in military field operations or on a construction site.

on the water wagon. wagon(def 14).

Origin of water wagon

First recorded in 1805–15

How can he remain a social animal, with the fellowship of his kind, and stay on the water-wagon?

The Old Game |Samuel G. Blythe
So you fell off the water-wagon, eh,—even in the watery city?

The Adventures of the Eleven Cuff-Buttons |James Francis Thierry
Next I heard of him he had "fallen off the water-wagon" and was reported to be celebrating the event in Tonopah.

My Adventures with Your Money |George Graham Rice
Wainwright was on the water-wagon—thanks to me and Timotea—and he was soon in clover with the government gang.

Rolling Stones |O. Henry

She was out on the prairie at night, miles away from any house, driving a water-wagon for the men to put out a prairie fire.

Her Prairie Knight |B.M. Sinclair, AKA B. M. Bower