Which of these two piston pumps can be offset from the top of the well?

The correct answer is that only the shallow well piston pump can be offset from the top of the well. Shallow well piston pumps are designed to be installed above ground, and they typically have the capability to operate effectively when offset from the actual water source. This is due to their design, which includes a suction line that can draw water from a well, even if the pump is not directly above it.

In contrast, deep well piston pumps, especially submersible types, are designed to be submerged within the well and operate under the water level. Their operation relies on being located at a specific depth to effectively pump water to the surface. If they were offset, it could lead to inefficiencies or inability to maintain prime, as the design is optimized for direct vertical operation from the sub-surface water source.

Therefore, only the shallow well piston pump has the flexibility to be installed at a distance from the well, allowing for various configurations in its installation without compromising its functionality.