What Is the Difference Between a Surface Pump and a Submersible Pump?

A surface pump is installed in a dry location outside a basin, tank, or well and draws liquid through suction piping. A submersible pump is installed directly in the pumped liquid. The main differences involve installation location, pumping method, suction requirements, space requirements, waterproofing and sealing, and maintenance access. 

If liquid collects in a sump, sewage tank, basement, construction excavation, or stormwater detention basin, a submersible pump may be the more suitable option. A surface pump may be considered when sufficient dry space is available for the equipment and the suction piping can be properly arranged. The final selection should be based on the liquid type, required flow rate and head, installation environment, and maintenance requirements.

What Are the Main Differences Between Surface Pumps and Submersible Pumps?

The main difference is that a surface pump operates outside the pumped liquid, while a submersible pump is designed to operate while submerged. The two pump types also differ in their suction requirements, space requirements, waterproofing, flood exposure, noise transmission, and maintenance access.

Why Are Submersible Pumps Commonly Used for Sewage and Drainage?

Submersible pumps are commonly used for sewage and wastewater transfer, construction dewatering, basement drainage, and flood control because they can be installed directly where the liquid collects. This reduces dependence on suction piping and priming and can also reduce the amount of dry equipment space required.

1. Reduced Dependence on Suction Piping and Priming

Because a submersible pump operates directly in the liquid, it is less dependent on suction lift, airtight suction piping, and priming than a surface pump that draws liquid through suction piping. For drainage applications where liquid collects in a sump, sewage tank, basement, or construction excavation, a submersible installation provides a more direct pumping arrangement.

Common installation locations include：

• Sumps
• Sewage tanks
• Basement drainage areas
• Construction excavations
• Stormwater detention basins
• Pumping stations

When a surface pump draws liquid through suction piping, the suction lift, airtightness of the piping, potential air ingress, and priming requirements must be carefully evaluated. The actual operating requirements depend on the pump type and system configuration.

2. Reduced Requirements for Dry Equipment Space and Suction Piping

A submersible pump can be installed directly inside a basin, tank, well, or flooded area. This reduces the need for a separate pump base and suction piping in a dry equipment area.
In basements, wastewater treatment facilities, stormwater pumping stations, and other space-limited locations, installing the pump closer to the liquid source can simplify the above-water piping and equipment layout.

3. Suitable for Areas Subject to Water Accumulation or Flooding

Surface pumps generally need to be installed in a dry area and protected from rainwater, standing water, and flooding. Submersible pumps are designed to operate while submerged and are therefore well suited to sumps, sewage tanks, and other locations subject to continuous or intermittent water accumulation.
Control panels, electrical connections, and other above-water electrical equipment must still be installed in suitable locations with appropriate protection against water ingress and electrical hazards based on site conditions.

4. Submerged Operation Can Reduce Some Noise Transmission

What Is IP68, and Why Is It Important for Submersible Pumps?

IP68 is an ingress protection rating that indicates the level of protection against dust and water ingress. The first digit, “6,” indicates dust-tight protection, while the second digit, “8,” indicates protection against continuous immersion in water under conditions specified by the manufacturer. 
Because a submersible pump operates directly in water or another pumped liquid, it requires appropriate waterproofing, sealing, and electrical insulation for submerged operation.
HCP submersible pumps are rated IP68 for submerged operating environments. The permitted immersion depth and operating conditions should be confirmed in the specifications and operating instructions for each product.

How Do HCP Submersible Pumps Reduce the Risk of Water Ingress?

HCP submersible pumps incorporate protective measures at the cable entry and mechanical seal, together with insulation treatment for the stator, to reduce the risk of moisture or pumped liquid entering the pump during submerged operation.

Key protective features include：

• Epoxy resin-sealed water-resistant cable base: Helps reduce the risk of moisture entering the pump along the cable.

• Mechanical seal: Provides a seal between the rotating shaft and stationary pump components, helping reduce the risk of pumped liquid entering the pump interior.

• Vacuum impregnation and oven curing of the stator windings: This process enhances electrical insulation and moisture resistance.

The actual construction and configuration vary by product series and model. Always refer to the relevant product specifications when selecting a pump.

How Should I Choose Between a Surface Pump and a Submersible Pump?

When choosing between a surface pump and a submersible pump, consider where the liquid is located, the suction conditions, available equipment space, flood exposure, and maintenance access. These factors help determine the more suitable installation method.

A surface pump may be suitable when sufficient dry space is available, the suction piping can be properly arranged, and direct access to the pump is preferred for inspection and maintenance.

A submersible pump may be more suitable when liquid collects in a basin, sump, sewage tank, basement, or low-lying area and needs to be pumped directly from that location. Submersible pumps are therefore commonly used for sewage and wastewater transfer, construction dewatering, basement drainage, and flood control.

Before selecting a pump, confirm the following：

1. Type of liquid to be pumped
2. Presence of solids, fibers, or sediment
3. Whether the liquid is corrosive
4. Required flow rate and head
5. Water level, basin or tank depth, and available installation space
6. Risk of water accumulation or flooding
7. Installation, piping, and maintenance requirements

HCP offers a range of submersible pump series for sewage and wastewater, construction dewatering, large-volume dewatering, flood control, aquaculture, and aeration applications. The appropriate series and model should be selected according to the liquid type, solids characteristics, required flow rate and head, and installation environment.

If the application, required flow rate and head, and installation environment have already been identified, refer to“How to Select the Right HCP Submersible Pump for Your Application” for further product selection guidance.