Which submersible pump is best, water-filled, or oil-filled?

As an Amazon Associate I earn from qualifying purchases.

A submersible pump, as the name, suggests functions when it is submersed inside the water, well or other containers. The pump comes in a hermetically sealed motor with a close-coupled body. Its plus side is to prevent pump cavitation due to high altitude variation between the pump and the fluid surface.

The best submersible pumps accelerate the water to the surface by converting the rotary energy into kinetic energy. As the impeller rotates, it accelerates the water through the diffuser, making it reach the surface. In this process, the kinetic energy further transforms into pressure energy. 

Which submersible pump is best, water-filled, or oil-filled?

Types of submersible pump

In submersible pumps, the motor cooling method generally utilizes a liquid instead of air, as the pumps are completely submerged underground inside the water. Based on this principle, the pumps are available in the two types of models. 

The one that uses water as a coolant and the other which uses oil as a coolant. Water-filled and oil-filled submersible pumps are considered effective in protecting the motors. Both these types have different features and characteristics depending on the purpose of usage. 

See Also: Best water hose

Difference between water-filled and oil-filled submersible pumps:

  • Electrical winding system

The electrical winding system plays a vital role in making the device operate through power. A PVC insulated wire is used in a water-filled submersible pump to prevent the water from getting inside. Even if a short circuit happens, the PVC wire can be repaired quite easily without any hassle.

The oil-filled submersible pump uses the copper enameled wire that allows smooth operation. However, if there is a short-circuit in the copper wire, repairing the damages is not easy and takes time. 

  • Bearing mechanism

The bearing mechanism reduces the friction between the rotating shaft inside the motors. Bush bearing is typically found in the water-filled submersible pumps. These are independent plain bearing that offers bearing surfaces for the rotary applications when water circulates.

The ball bearing carries the operations in the oil-filled submersible pumps. Here oil acts as a lubricant for the ball to support the axial and radial loads and reduce the friction.  

  • Pump sealing

In the submersible pumps, the sealing should be robust and done properly to avoid major functioning problems. If there is any damage to the water-filled submersible pump’s seal, it will still operate without creating any problems. This is because the PVC wires are waterproof. 

While in oil-filled submersible pumps, if the seal is damaged, plenty of problems arise. When the water enters, it will instantly create oil leakage followed by damaging the ball-bearing, which ceases the operation. Sometimes, it can also cause a short-circuit if the wire enameling is weak. 

  • Water contamination

Water contamination is a problem noticed in submersible pumps. In water-filled pumps, chances of contamination are less even if water breaks through the seal. Only if some chemical get associated with the water, contamination takes place. 

Contamination is seen more in an oil-filled submersible pump. In case the seal is damaged, water will get inside quickly, and it gets mixed with the oil coolant. The chances are high with the oil contaminating the water. 

  • Energy efficiency

Energy efficiency is another parameter that demarcates the difference between oil-filled and water-filled submersible pumps. The oil-filled pumps are typically more energy-efficient, which helps to reduce the electricity bills. 

On the contrary, water-filled pumps are not much energy efficient when compared to oil-filled ones. 

  • Rusting

The phenomenon of rusting is mainly associated with a water-filled submersible pump. If the water-filled pumps are not used for a long period, there are good chances of rusting inside the pump as water is the coolant here. The motor will not perform even when the power is supplied. 

In an oil-filled pump, rusting doesn’t take place since oil is used as a coolant. The motor will give a smooth service even if it is not operated for a long time. 

  • Application

The application of the water-filled and oil-filled submersible pump is different. The water-filled submersible pump is lightweight and compact in structure. It is considered ideal for small residential requirements and usage. 

While the oil-filled submersible pump is preferable for use in the big residential, commercial, and industrial sectors. This robust built-finish makes it perfect for heavy-duty usage. 

  • Regions

There is another major difference between both types of submersible pumps. The oil-filled pump is regarded as the best to be used in cold regions. When the temperature goes beyond the freezing point, the oil coolant doesn’t freeze easily. 

The water-filled pump works well in dry and tropical regions where the temperature always remains high almost through the year. 


There are several factors to evaluate when it comes to select between the water-filled and oil-filled submersible pump. Both these pumps have their own irreplaceable strength and downsides, which greatly varies upon the relevance and end-purpose of use. 

Most importantly, high-quality and best submersible pumps need to be selected, whether it’s a water-filled or oil-filled pump. 

Sophie Turner
Home Accessories Tips