Series Pump Combination Total Head
Series Pump Combination Total Head
When a single pump cannot generate enough head for a duty — a long pipeline or a tall vertical lift, for example — engineers often stage two pumps in series, where the discharge of the first feeds directly into the suction of the second. Because the same fluid passes through both machines in turn, the flow rate is unchanged but the head each pump adds is stacked on top of the other. This is the standard trick behind multistage pumps and booster stations alike, and it is important not to confuse it with parallel staging, which instead adds flow at constant head — using the wrong combination rule when sizing a booster station leads to a system that badly misses its target operating point.
For pumps in series at the same flow, the combined head is the sum H_total = H1 + H2. where H_1p is the head rise across the first pump and H_2p is the head rise across the second pump, both at the shared flow rate.
Inputs
H_1p := 20 m=20 m
H_2p := 18 m=18 m
Since the discharge of the first pump feeds the suction of the second, the flow is common and the heads simply add.
H_total := H_1p + H_2p=38 m
Results
The series-combined head is always at least as large as either pump alone, which is exactly the point of the arrangement — here the combination delivers substantially more head than either machine could alone at the same flow. In practice each pump must be checked against its own maximum allowable working pressure, since the second pump in the string sees the discharge pressure of the first added to its own.
Assumptions & limitations
- Both pumps operate at the same flow rate (series arrangement).
- Pump curves assumed compatible so neither is driven into an unstable region.
- Piping and fitting losses between the two pumps are neglected.
- Does not check individual pump pressure ratings against the combined discharge pressure.