When the volume of sewage to be raised is small or the height it is to be elevated is great, the piston type of pump will give the best results. The sewage should be screened, however, before entering the suction pipe of this type of pump, to prevent the entrance of anything that might have been carelessly introduced into the drainage system which might interfere with or injure the working parts of the pump. Piston pumps are suitable only for comparatively clear sewage, and should not be used where coarse, insoluble materials are discharged into the drain or where chemicals are discharged that might cut the valve seats of a pump.

Piston pumps may be electrically driven or operated by steam, and may be made to operate automatically or to be started and stopped by an attendant. The manner of installing a piston pump ejector is similar to the manner of installing a centrifugal pump ejector, with the single exception that a piston pump may be located at any convenient point not over twenty-eight feet above the level of the sump. When steam is the motive power, the pump may be connected up to work automatically in the same manner as a feed-water pump and receiver.