Vertical Dry-Pit Pumps
Dry-pit pumps with external bearings include most small, medium, and large vertical sewage pumps, most medium and large drainage and irrigation pumps for medium and high heads, many large condenser circulating and water supply pumps, and many marine pumps. Sometimes the vertical design is preferred (especially for marine pumps) because it saves floor space. At other times, it is desirable to mount a pump at a low elevation because of suction conditions, and it is then also preferable or necessary to have the pump driver at a high elevation. The vertical pump is normally used for large capacity applications because it is more economical than the horizontal type, all factors considered.
Many vertical dry-pit pumps are basically horizontal designs with minor modifications (usually in the bearings) to adapt them for vertical-shaft drive. This is not true of small and medium-sized sewage pumps, however. In these units, a purely vertical design is the most popular. Most of these sewage pumps have elbow suction nozzles (see Figures 102 through 104) because their suction supply is usually taken from a wet well adjacent to the pit in which the pump is installed. The suction elbow usually contains a handhole with a removable cover to provide easy access to the impeller.