The two-stage pump impellers operate in which configurations?

• A. Series
• B. Parallel
• C. Series or Parallel
• D. None

Answer: (C)

Two-stage impellers can be used to increase either pressure (head) or volume (flow) depending on how they are connected in the pump and piping. When the water passes through one impeller and then directly into the second, the pressure from both stages adds up while the flow remains essentially the same as a single stage—this is series operation. If the inlet splits so each impeller handles part of the total flow and their discharges are combined, you can achieve a higher overall flow at roughly the same head—this is parallel operation. A two-stage pump is designed to be able to perform in either arrangement, depending on the system requirements, which is why both configurations are listed as possibilities.