"The day the pump ran dry," referred to in Robert Phileo's editorial in the August 1973 ACI Journal, was a disaster. How did it happen? Some of the details of that particular job on a concrete deck have been reported to the editors by A. T. Hersey or E. L. Conwell Company. Mr. Hersey was the inspector of the job. A lightweight concrete of 4000 psi design strength, with unit weight of 113 points per cubic foot, four inch slump and four to six percent air was to be pumped 20 feet vertically and about 125 feet horizontally. The concrete mix had been designed for placement by bucket or buggy and was to be made with one inch maximum size expanded shale coarse aggregate; silica sand was to be used for the fine. Because of placement conditions were difficult the contractor decided to pump the concrete and, with the approval of the architect, the mix was modified by decreasing the coarse aggregate and increasing the sand and cement content. Job troubles began almost immediately. The mix would not go through the four inch pipe initially used. Disaster fell the next day when a different pump was brought to the job and the mix would not move at less than an eight inch slump. The slump loss in the line sometimes ran as much as four inches, showing that although the lightweight aggregate stockpile had been kept wet the aggregate was taking up water from the mix during the pumping. What had gone wrong? Mr. Hersey felt that part of the trouble was that the relevant ACI standards had not warned against adjusting the mix beyond limits set in ACI 211.2. He advocated that ACI standards should require that pumping not be permitted unless the concrete will pump at the air and slump specification limits measured at the pump.