Use a submersible pump for drainage, deep water sources and applications where the pump can remain underwater. Use a surface/self-priming pump when service access and shallow suction are more important.
Submersible pumps
Submersible pumps operate with the motor below the water surface. Domestic drainage models are common for flooded cellars, sumps and tanks, while borehole pumps serve much deeper water sources.
Because they push water rather than relying on suction from above, submersibles avoid many priming limitations.
Surface pumps
A surface pump sits dry and draws water through a suction line. Self-priming models are common for irrigation and rainwater reuse.
Suction lift is physically limited, so the vertical distance from water surface to pump matters. DAB publishes a maximum suction depth of 8 m for the Esybox Mini 3.
Maintenance and access
Surface pumps are easier to inspect and service because they remain accessible. Submersibles may need to be lifted out of a tank or well for maintenance.
For emergency flood drainage, portability and automatic switching can matter more than service access.