Pumps and Systems

Caisson Well Submersible Pumps: Features, Selection and Installation

Caisson well submersible pumps work submerged to draw water quietly from large-diameter shallow wells and tanks. Learn about float switch models, selection criteria and installation.

ORFA Technical TeamUpdated: Oct 30, 20264 min read

In rural areas and homes with gardens, water is often supplied from caisson wells: large-diameter, usually hand-dug wells close to the groundwater level. A caisson well submersible pump, designed for these wells and for water and rainwater tanks, works submerged; it has no suction problems, runs quietly and is easy to install.

In this article you will find what caisson well submersible pumps are, where they are used, what to consider when selecting one and installation tips.

What Is a Caisson Well Submersible Pump?

Caisson well submersible pumps are compact pumps that operate submerged together with their motor, designed to draw water from large-diameter shallow wells, tanks and cisterns. Because the pump is under water, there is no suction lift limit and no initial priming is needed.

On float switch models, the float stops the pump automatically when the water level falls below a certain point, preventing dry running; the pump restarts when the level rises.

Applications

Caisson wells: Water supply from large-diameter wells close to the groundwater level.
Water tanks: Transfer from clean water and rainwater tanks.
Agricultural irrigation: Garden and field irrigation.
Domestic water supply: Household water, particularly in rural areas.
Industrial use: Supply of process and service water.
Streams and lakes: Drawing water from shallow sources (with suitable filtration).

Technical Features and Benefits

Wide range of flow and head: Models are available for different needs.
Float switch options: Provide level control and dry-run protection.
Quiet operation: Working under water, the pump is very quiet.
Corrosion-resistant materials: Some models have a stainless steel outer casing for long life.
Easy installation: No suction line or priming required.
Flexible mounting: Some models can be installed horizontally or vertically depending on the well.

Selection Criteria

Criterion	Why it matters
Well diameter	The pump must fit comfortably and be removable for maintenance.
Well depth and water level	The dynamic water level is the starting point for the head calculation.
Required water quantity	Determines the flow; the yield of the well must not be exceeded.
Well bottom and water cleanliness	Sand and mud affect the installation height and the pump’s service life.
Motor cooling	Continuously running pumps need adequate motor cooling.
Power supply	Single-phase (220-230 V) or three-phase (380-400 V) according to the supply.

When Is a Cooling Sleeve Needed?

Submersible motors are cooled by water flowing along their casing. In large-diameter caisson wells, if the pump operates where water does not flow past the motor, the motor may not be cooled sufficiently. A cooling sleeve (shroud) around the motor then forces water to flow over the motor surface. Follow the manufacturer’s installation instructions for when and how it is required.

Installation Tips

Do not stand the pump on the well bottom; suspend it high enough to avoid drawing in sand and mud.
Suspend the pump from a stainless steel safety rope, not from the power cable or the pipework.
On float switch models, check that the float can move freely without catching on the well wall or pipe.
Fit a check valve in the discharge line to prevent backflow when the pump stops.
Have the electrical connection made by a qualified electrician with suitable motor protection and earthing.

Tip: Knowing the lowest water level of the well in summer lets you set both the pump’s installation depth and the head calculation correctly.

Frequently Asked Questions

What is the difference between a caisson well pump and a deep well submersible pump?

Caisson well pumps are compact pumps designed for large-diameter shallow wells and tanks. Deep well submersible pumps are slim and long so that they can be lowered into narrow, deep boreholes.

What does the float switch do?

It stops the pump when the water level falls below a certain point, preventing dry running, and restarts it when the level rises.

Can the pump be placed on the bottom of the well?

This is not recommended. Sand and mud from the bottom are drawn into the pump, causing wear and clogging. Suspend the pump at a sufficient height above the bottom.

Conclusion

Caisson well submersible pumps are a quiet, practical and reliable solution for water supply from large-diameter shallow wells and tanks. Choosing a model that suits the well dimensions and water demand, installing it correctly and protecting it against dry running ensure a long service life. Explore the different submersible pump types in our Submersible Pumps product group.

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