PUMP SIZE P047
Three numbers determine the size of a centrifugal pump. The numbers describe:
- The inside diameter of the inlet piping in either inches or millimeters.
- The inside diameter of the outlet piping in either inches or millimeters.
- The diameter of the largest impeller you can put on the pump, not necessarily the one that is on there now.
So what do the numbers describe on a 3 x 2 x 13 pump?
- The largest number is always the impeller size.
- You can identify the other two if you recognize that the outlet cannot be larger than the inlet. If it were you could pump out more than you took in, and that would be stupid*, so:
- 3 inches is the size of the inlet
- 2 inches is the size of the outlet
- 13 inches is the size of the largest impeller you can put on the pump.
Some people use only the outlet pipe size to describe the pump and refer to it as a six-inch pump.
Remember also that this is the nominal size only and does not help you to determine the capacity of the pump.
* one exception to this statement is found with some sewage lift station pumps where the inlet of the submerged pump is smaller than the outlet to prevent clogging.