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What is Wellpoint Dewatering?

A wellpoint dewatering system is made up of a number of wells that are shallow, also known as wellpoints. They are placed at a predetermined depth and spaced appropriately around an excavation.

The wellpoints connect to the surface via a riser and then to a common main pipe through a flexible.

This flexbow has an adjustable pushfit valve that allows for the control of water and air entering the system. It is known as trimming.

The main pipe connecting to the header is connected to a pump that dewaters wells.

SLD’s Wellpoint Dewatering Systems can be used in a variety of ways.

They can be used for controlling groundwater levels during excavations to create dry and stable working environments. SLD’s Wellpoint Dewatering Systems can handle very low flows of silty and coarse sands, as well as larger flows of gravel and coarse sands.

SLD Pumps and Power can be used to rent multi-stage rental solutions for excavations that are too deep to support a single stage dewatering system.

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Wellpoint System Design

A wellpoint systems is a collection of smaller-diameter wellpoints that are installed at pre-determined depths (usually 23ft deep) and located near centers.

It is easy to set up and can handle a variety of flows.

The wellpoints are connected to a common header via a swing joint that runs to a vacuum assisted centrifugal pump

Three functions are the core of the pump:

Primes the system and creates a vacuum

Separates water/air

Pump water until it reaches the point of discharge

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Different types of Wellpoint

Every installation needs to have wellpoints.

There are two types:

(i) The self-jetting point

They are also known as self-jetting because they can be used without the need for a placing tube.

The riser and wellpoint are made of metal and are therefore rigid. They are connected to the bottom end of the riser pipe.

This type could be reused again.

The water supply to the riser and wellpoint is high-pressure water.

Below the wellpoint screen is a hollow shoe for jetting.

A horizontal pin is located near the lower end of your shoe. Above the pin is a lightweight, loose-fitting ball.

The water pressure applied to install the wellpoint causes the ball to be displaced downwards. However, the pin keeps the ball in the jetting shoe.

The ball is sucked up onto a shaped, spherical stating by the vacuum applied to the pump. This seals the lower end.

This ensures that water cannot enter the screen from the ground below.

To minimize air intake during maximum drawdown, the unperforated riser should be extended to the end nearest the screen’s lower edge.

Although the self-jetting wellpoint can still be extracted and reused, it is quite common for riser pipes to become damaged during extraction. They will need to be straightened or replaced before being reused.

The wellpoint screens might need to be ‘desanded’ before they can be reused.

(iii) The disposable point.

The wellpoint and riser are usually made of plastic and therefore inert from corrosion.

These are installed using a hole puncher or placing tube, and similar high-pressure water jetting techniques to install the self-jetting point.

Although manufactured plastic wellpoints are known for a while,

Current practice is to use low-cost thin walled convoluted uPVC land drainage pipe with woven mesh stocking to create disposable wellpoints.

This creates a filter that is effective in all soil types, even those with very silty.

The riser, which is typically made from uPVC ducting, should be extended to the end of the screened length.

Seal the bottom end of your disposable wellpoint.

The riser pipe should be approximately 6 m in length, but it is possible to make it longer.

Disposable wellpoints cannot be recycled, but plastic riser pipes may sometimes be salvaged for future use.

For long-term pumping duties, the disposable wellpoint is ideal.

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