Milwaukee's 1891 North Point Pumping Station and Water Tower)

(3D Satellite, the water tower for the standpipe still exists)

Screenshot,via live_videos  Or search for "Machines of Milwaukee" in nmih

The North Point Pumping Stations was the first installation of an EP Allis triple-expansion steam engine designed to pump water. It's claim of being the most efficient in the world was contested by others. But the claim was proven to be true by a professor from Cornell.

Screenshot,via live_videos  Or search for "Machines of Milwaukee" in nmih

The controversy and verification of its efficiency proved to be good advertisement and over 100 water pumping engines were built including some used in the Chicago Avenue Pumping Station.

Screenshot,via live_videos  Or search for "Machines of Milwaukee" in nmih

ASME
[This photo of the 1888 Flushing Station shows the water tower in the left background.]

Screenshot
Virtual Museum: Inside the Largest Operable Stationary Steam Engine in North America

The Allis Chalmers expansion engine located in the former site of the People's Water Company of Phillipsburg New Jersey, Presently holds the title of the largest operable stationary steam engine in North America.The engine also became the first American triple Expansion waterworks engine to be operated in preservation when it was demonstrated on steam in 2018. Standing at almost six stories tall, it along with the rest of the facility was constructed in 1913 to supply six million gallons a day of water to the city of Phillipsburg, today it remains as a remarkably complete example of a medium sized early twentieth century waterworks.

Presenter/guide Philip Beard is one of two Project leads of the Phillipsburg Triple restoration project, under the Friends of the New Jersey Transit heritage center. He is a recent graduate of Pratt Institute where he spent time learning from Conrad Milster in the Historic Pratt power plant.

The high-pressure cylinder is 24" and uses steam at 125-150 psi. The intermediate-cylinder is 36" and uses steam at 40 psi. I don't remember him giving the bore for the low-pressure cylinder. I do remember him saying the pressure was 0. At first, that shocked me. But then I remembered that the exhaust steam is run through a condenser. Thus the other side of the low-pressure piston has a negative pressure, that is a partial vacuum. The use of a vacuum is one reason why these pumps were so efficient. Another reason they were so efficient is that the speed is controlled by the duration of the valve opening rather than the steam throttle. That is, the two-ball governor controls the valve of the high-pressure cylinder and the engine is run with a wide open throttle. When running with a heavy load, the admittance valve is held open during most of the piston's travel. When running with a light load, the valve snaps shut early in the piston's travel.