Dewatering Pump Basics | Function, Types & Applications

What does “dewatering” mean, and what role do dewatering pumps play?

What is a Dewatering Pump?

Dewatering pumps are designed to remove water from one location and transfer it to another. That might sound simple, but it’s one of the most important tasks on any jobsite dealing with groundwater, rainwater, or process water that needs to be moved fast and efficiently.

In short: if you’ve got excess water where it shouldn’t be, a dewatering pump is what you’ll want to use.

Working Principle of Dewatering Pumps

At the core of most dewatering pumps is a simple concept: convert mechanical energy into hydraulic energy to move water. How they do this depends on the pump type, but let’s focus on centrifugal dewatering pumps (the most common kind).

These pumps use an impeller mounted on a rotating shaft. As the impeller spins, it creates centrifugal force, pushing water outward into the pump casing and out through the discharge. The resulting low pressure at the impeller eye draws in more water from the source.

This cycle continues, as long as the pump stays primed and has adequate power. Motor speed, torque characteristics, and the torque curve of the motor all play a role in how effectively water is moved. You’ll usually find the motor operating in the constant torque region for most dewatering tasks. This allows consistent movement of fluid across varying system heads.

The applied voltage, motor speed, and the shape of the torque speed characteristics all contribute to performance. When selecting a pump, engineers look at how the curve represents system resistance compared to pump performance at a given speed.

TIP: Don’t forget to account for inlet conditions; poor suction can cause cavitation, even in well-designed systems.

Common Applications

You’ll find dewatering pumps in all kinds of industries:

• Construction sites – Keeping foundations dry during building
• Quarries and mining operations – Handling ground and surface water
• Municipal systems – Flood control and wastewater bypass
• Industrial operations – Slurry and sludge handling

Not all water is clean water. Make sure your pump is built to handle the type of fluid you’re moving, especially if solids are involved.

Types of Dewatering Pumps

There are a few different kinds of dewatering pumps. Here’s a quick look at the main types.

1. Centrifugal Pumps

These are some of the most common dewatering pumps out there. Like we mentioned before, they use a spinning impeller to create centrifugal force, which moves water through the system. Centrifugal pumps are great for moving large volumes of water quickly, as long as there aren’t too many solids in the mix.
They’re often used in construction, mining, and municipal applications when fast, consistent water movement is the priority.

2. Submersible Pumps

Submersible pumps are probably the most widely used for general dewatering. These pumps are dropped directly into the water, and their motor is completely sealed so it can keep running while submerged.

Because they push water rather than pull it, they’re great for deeper pits, flooded basements, or any place where suction isn’t practical. They’re also quieter since they’re underwater, and tend to require less setup than some other options.

Caution: Do not lift or lower the pump by the power cord, as it is sealed connection. Should the seal be compromised, liquid will enter the motor causing failure. Always use a rope or chain attached to the lifting lug or device.

3. Trash Pumps

Trash pumps are made for the messier stuff: mud, rocks, leaves, and anything else that might be floating around in stormwater or runoff. These are basically centrifugal pumps with larger openings and tougher internals, so they can handle solids without clogging up.

You’ll often see them on construction sites where the water isn’t exactly clean. They’re not built for precision, but they’ll keep things dry and moving.

4. Diaphragm Pumps

Instead of impellers, these pumps use reciprocating diaphragms to move fluid. They’re slow and steady but excellent when pumping sludge, slurry, or abrasive material. The most common diaphragms pumps are air operated and therefore intrinsically safe for explosive environments, however an air source is required and the cost of air should be considered. 

5. Wellpoint Pumps

Used to dewater shallow aquifers, wellpoint systems use a series of small wells connected to a header pipe and a vacuum pump to draw water out of the ground.

Selection Tips from the Field

• Flow rate – Know how much water you need to move per hour
• Head pressure – Don’t overlook how high or far the water needs to be pumped
• Fluid type – Solids? Chemicals? Sludge? That affects pump material and design
• Portability – Some sites need pumps that move frequently, others want a permanent install

Another tip is to avoid undersizing your pump. It might work for a day but it won’t last. Aim for the right fit – not the smallest one.

PumpWorks: Your Partner in Precision Pump Solutions

If you’re selecting a new dewatering pump or upgrading for better performance, PumpWorks is here to help. Our pump manufacturer team understands torque curves, output shaft performance, constant power regions, and everything else there is to know.

We work directly with our customers to specify pumps that suit the application…not the catalog. If you need guidance on choosing between several types or understanding how your motor’s constant torque region affects system performance, talk to us!

Reach out to PumpWorks today.