A well point pump system functions by creating a partial vacuum that draws groundwater out of the soil, effectively lowering the water table in an excavation area.
Understanding the Mechanism
At its core, a well point pump works by leveraging atmospheric pressure. Here's the breakdown:
- Creating a Vacuum: The pump connects to a network of shallow wells called "wellpoints" via a pipe called a "header main." The pump unit itself creates a partial vacuum in the header main, which draws up the water.
- Water Inflow: This vacuum causes the water table around the wellpoints to rise slightly towards the wellpoints and then be drawn up through them into the header main.
- Collection and Discharge: The collected water flows through the header main back to the pump, where it is then pressurized and discharged at a designated point away from the excavation site.
Think of it like using a straw: when you suck (create a vacuum) at one end, the liquid is drawn up the straw. A well point pump does this on a larger scale to remove groundwater.
System Components
A typical well point system includes:
- Wellpoints: Small diameter, screened pipes installed below the water table.
- Header Main: A horizontal pipe connecting the wellpoints to the pump.
- Pump Unit: The heart of the system, creating the vacuum and discharging the water. This often includes a vacuum pump and a centrifugal pump working together.
Installation Methods
Wellpoints need to be strategically placed around the area where dewatering is required. Typically, wellpoints are installed around the perimeter of an excavation, or parallel to a pipeline trench. Common methods for installing wellpoints include:
- Jetting: Using high-pressure water to bore a hole and seat the wellpoint.
- Auguring: Using a helical screw-like tool to drill the hole.
- Traditional Drilling Techniques: Utilizing standard drilling rigs, especially in denser soils.
| Installation Method | Description | Best Used For |
|---|---|---|
| Jetting | Uses water pressure to bore and install | Sandy or silty soils |
| Auguring | Drills a hole using a helical tool | Softer cohesive soils or mixed conditions |
| Traditional Drilling | Employs standard drilling rig technology | Denser soils, rock formations, or deeper wells |
Practical Application
Well point systems are widely used in construction projects to lower the groundwater level, creating a dry and stable environment for digging foundations, installing pipelines, or other below-ground work. This dewatering prevents issues like:
- Excavation collapse due to saturated soil.
- Flooding of the work area.
- Difficulty in compacting soil.
By maintaining a lower water table, well point pumps ensure project safety and efficiency.
