Dewatering pumps, as the name implies, are pumps that are used to remove unwanted water, using centrifugal force. Dewatering pumps can operate by either of two means; they can be submerged into the water and pump out the unwanted water once it rises to a certain extent or they can be placed above ground while some tiny tubes are put into the water, then they pump out the unwanted water through those tubes.
There are different types of pumps that could serve as dewatering pumps but the most common ones are the submersible pumps, well-pointing piston pump, end suction pump and trash pumps.
Submersible pumps have hermetically sealed motors that are coupled closely with the body of the pump, thus allowing the pump to be submerged either totally or partially without the motor being damaged. The propellers of submersible pumps convert their rotational energy into kinetic energy then further into pressure which pushes water to the surface through a discharge pipe. The submersible dewatering pumps are able to handle abrasives like sand, small stones etc, depending on the type of impellers they contain. If the impellers are open impellers, then the pump can only transport water and small particles, but if the pump contains closed impellers, then it can be used to pump out muddy water that may contain larger solid particles.
The advantages of the submersible dewatering pumps include; they do not take up a lot of operating space, and since they are already in water, do not require priming before they start. They are also seemingly noiseless due to their underwater location and are versatile enough to handle solid particles as well as liquid. The major disadvantage of the submersible dewatering pump is that, because it is placed under water, the seal is susceptible to corrosion which could allow water to enter the motor and lead to malfunctions. The underwater positioning of the submersible pump also makes it difficult to get to the seal in order to check and repair the motor when necessary.
The end suction pump is a type of dewatering pump that uses centrifugal force to bring the water up to the surface and out through the discharge outlet. This dewatering pump needs to be primed before it can be used, but there are self priming types available. The disadvantages of the self priming end suction pump include; the priming process can be interrupted by vacuum leaks, the pump needs to be placed very close to the water source. End suction pump can only be used for dewatering in situations where the distance between the water surface and the suction hose is less than 25 feet.
The well point piston pumps self priming positive displacement pumps that can also be used for dewatering. They are suitable for moving thick fluid and even abrasive fluids, which makes them the best option for dewatering muddy areas like construction areas. The major advantage of this type of dewatering pump is that they can pump fluid at a constant flow rate, no matter the force or pressure. The operation and maintenance cost of using the well-point piston has to be the major disadvantage of this dewatering pump.
Trash pumps are dewatering pumps that are most suitable for transporting muddy water, sand and general debris. They suck up the dirty water, then filter out the dirt and debris from the water. There are three types of trash pumps; the semi-trash pump which can only transport smaller particles, the centrifugal trash pump and the diaphragm trash pump which is suitable for moving water containing larger particles and debris.