The terms submersible and immersible may sound interchangeable, but in the world of water pumps these two are notably different. The submersible pump is a heavy-duty pump for heavy-duty jobs. The immersible pump is a more cost-effective option for lighter-duty applications. Let’s further discuss how these two types of water pumps differ in where and how they generally operate.
Submersible Water Pumps
Submersible water pumps have many industrial uses. They are hardy, corrosion-resistant, and available as explosion-proof. Completely enclosed, the motor is integral with the pump and designed to run continuously submerged in water. These pumps are built with frames that are precision machined to ensure a tight fit between every component of the motor and pump. Submersible pumps typically have a specially designed dual seal design where the outer seal is lubricated by the pumpage and the second seal is housed in an oil bath chamber in or below the motor housing for seal lubrication. This chamber may also contain the motor drive end bearing and may also contain a moisture probe, that when properly connected, signals the motor to shut down in the event that water leaks into it. Alternatively, in the motor housing a moisture sensing monitor probe may also be present in order to detect moisture entering the housing.
Although built for continual submersion, these water pumps can also be placed in dry environments that only flood under unusual conditions. Based on their design, the motor may require an external source of liquid for cooling or have an intermittent run time rating when run un-submerged. These pumps are typically used in applications where they help manage sewage, storm and drainage water, oily water and other effluents.
Immersible Water Pumps
Immersible water pumps have motors that are built with the intent that they may be submerged and continue running in the event of the rare flood, but they are not meant to be submerged under normal everyday circumstances. These motors are built specifically to operate in a dry environment and can be retrofitted where a vertical solid shaft motor was used. They are built with a sealing system that can withstand being submerged under up to 30 feet of water for up to two weeks. Immersible water pump motors are designed with a drive endplate packed with moisture-resistant grease, instead of the oil chamber found in a submersible water pump. Immersible water pumps are often easier to service, less expensive to purchase and operate. They are appropriate for use in underground storm water pump stations where the pump gallery is designed to function as an incidental secondary wet well for the very rare major flooding event. After this motor is immersed, it must be removed for inspection and a bearing change.
When choosing a pump, the type of conditions under which the pump will be subjected will best dictate the type of pump required. Immersible pump motors are more cost-effective for the rare must-run flooding situation, but if the motor will be continually submerged in water, a submersible water pump is the correct option.