How to Construct a Tube Well: A Step-by-Step Guide

A tube well is a narrow, deep shaft drilled into the ground to access underground water from aquifers. It’s one of the most reliable sources of groundwater for agricultural irrigation, dairy operations, and domestic use. But constructing a tube well isn’t as simple as just drilling a hole – it involves a precise sequence of steps, from site selection and drilling to installing casings and screens, followed by thorough well development. Each stage must be carried out carefully to ensure optimal water yield, longevity, and protection from contamination. Let’s walk through the entire process.

What is a tube well? 🔗

A tube well is essentially a borehole fitted with pipes (casings) and a filtering mechanism (screen) that allows water to flow in from underground aquifers while keeping out sand and debris. Unlike open dug wells, tube wells can reach depths ranging from 30 metres to over 300 metres, depending on the type of aquifer being tapped. They are classified based on depth (shallow or deep), construction method (drilled, driven, or jetted), and the type of aquifer they access – whether it’s a water table aquifer, a semi-artesian aquifer, or a fully artesian one.

Tube wells are widely preferred in agriculture because they provide a sustained yield of water even during drought years and generally tap into better-quality groundwater compared to surface sources. However, their construction requires specialised equipment and skilled labour.

Step 1: Site selection and hydrogeological survey 🔗

Before any drilling begins, the first critical task is choosing the right location. This involves a hydrogeological survey to assess the availability and depth of groundwater in the area. Factors such as proximity to existing wells, the nature of underground rock formations, the expected depth to the water table, and any potential contamination sources (septic tanks, chemical storage, etc.) all play a role in site selection.

Geophysical methods like electrical resistivity surveys can help identify promising aquifer zones. Local well records and geological maps from agencies like the U.S. Environmental Protection Agency or regional groundwater authorities provide valuable baseline data. In India, the Central Ground Water Board publishes district-level hydrogeological data that can guide site decisions for agricultural tube wells.

What to look for during site assessment 🔗

Key parameters include the expected aquifer depth, estimated yield, water quality indicators, and the geological profile of the area (sandy, gravelly, clay-rich, or rocky). The site should also allow adequate space for the drilling rig, support vehicles, and material storage. A poorly chosen site can result in low yield, high drilling costs, or even a dry borehole.

Step 2: Drilling the borehole 🔗

Once the site is finalised, the actual drilling begins. The choice of drilling method depends on the geological conditions, the target depth, and the available equipment. The two most widely used methods for tube well construction are cable tool (percussion) drilling and rotary drilling.

Cable tool (percussion) drilling 🔗

This is one of the oldest drilling techniques, with roots going back over 4,000 years to ancient China. In this method, a heavy drill bit is attached to a steel cable, which is repeatedly raised and dropped into the borehole. The repeated impact crushes the rock and soil into fine particles, which mix with water in the hole to form a slurry. This slurry is then removed using a bailer – a hollow tube with a one-way check valve at the bottom.

Cable tool drilling works well in unconsolidated materials and soft rock formations. It is slower than rotary drilling, but has distinct advantages: low equipment cost, simple and rugged design, and the ability to operate with minimal maintenance. The driller can also identify aquifer zones more easily because the bailer allows real-time monitoring of water levels and flow rates during drilling.

Rotary drilling 🔗

Rotary drilling uses a rotating drill bit attached to a drill string to cut through geological formations. A drilling fluid – usually a bentonite-based mud – is pumped down through the drill string and back up through the annular space between the drill pipe and the borehole wall. This fluid serves multiple functions: cooling and lubricating the bit, stabilising the borehole walls, and carrying cuttings to the surface.

Rotary drilling is significantly faster than cable tool drilling and is the preferred method for deep tube wells. However, it requires more complex equipment, larger quantities of water, and skilled operators. There are several sub-types, including direct rotary, reverse circulation rotary, and air rotary (which uses compressed air instead of mud and is ideal for hard rock formations).

Step 3: Maintaining the well log 🔗

Throughout the drilling process, maintaining a detailed well log is essential. A well log is a written record of every geological formation encountered during drilling, noting details such as depth, material type (clay, sand, gravel, rock), colour, grain size, and any water-bearing characteristics observed at each interval.

For example, an entry might note that the first 5 metres consisted of brown topsoil and clay with no water, followed by fine sand with slight moisture between 5 and 12 metres, and then coarse sand and gravel with strong water flow from 12 to 20 metres. This record is used to make critical decisions about where to place casings and screens. It also becomes an invaluable reference for future pump selection, well maintenance, and troubleshooting.

The Ontario Ministry of the Environment’s well construction guidelines emphasise the importance of well records for regulatory compliance and long-term well management. Maintaining accurate logs is equally important under Indian groundwater regulations.

Step 4: Casing installation 🔗

Casing refers to the pipe installed inside the drilled borehole to prevent the walls from collapsing and to protect the well from surface contamination. It forms the structural backbone of the tube well. Casing materials are typically steel or PVC, with the choice depending on well depth, geological conditions, and budget.

Key considerations for casing 🔗

The casing diameter must be large enough to accommodate the pump that will be installed later. Common diameters range from 100 to 150 mm (4 to 6 inches) for domestic and small agricultural wells, though larger operations may use 200 to 250 mm (8 to 10 inch) casings. The casing must extend above the ground surface – usually by at least 30 cm – to prevent surface water from entering the well.

Joints between casing sections must be properly sealed to prevent contamination. In cable tool drilling, casing is often advanced simultaneously with drilling. In rotary drilling, it may be installed after the borehole has been completed to the target depth. The annular space – the gap between the casing and the borehole wall – is typically sealed with cement grout or bentonite to block contaminant pathways from the surface.

Step 5: Screen installation 🔗

The well screen is arguably the most important component of a tube well. It is a slotted or perforated section of pipe placed at the aquifer level that allows groundwater to enter the well while filtering out sand and sediment. As the Lifewater drilling manual puts it, the screen is the most important single factor affecting a well’s efficiency.

Choosing the right screen 🔗

Screen selection involves matching the slot size to the grain size distribution of the aquifer material. If the slots are too large, sand will enter the well and damage the pump. If they’re too small, they restrict water flow and reduce yield. A sieve analysis of aquifer samples collected during drilling guides this decision.

The screen length also matters. Longer screens generally produce higher yields but may draw water from zones of varying quality. The goal is to balance productivity with water quality. Screens are typically made of stainless steel, PVC, or galvanised iron, depending on the chemical characteristics of the groundwater and the well’s expected lifespan.

Step 6: Gravel packing 🔗

In many tube wells, a gravel pack (also called a filter pack) is placed in the annular space surrounding the well screen. This layer of clean, graded gravel serves as an additional filter that prevents fine aquifer particles from entering the well and clogging the screen.

According to the Ontario well construction regulations, the annular space around the screen must be filled with clean, washed gravel or sand from the bottom of the screen to at least the top of the screen. The gravel pack also stabilises the formation around the borehole, reducing the risk of collapse and improving the hydraulic connection between the aquifer and the well.

Gravel packing is especially important in wells drilled through fine-grained aquifers (fine sand or silt), where the natural formation material alone cannot adequately prevent sand entry.

Step 7: Well development 🔗

After the casing, screen, and gravel pack are in place, the well must go through a process called well development. This step removes drilling fluids, fine particles, and any residual mud cake from around the screen area, maximising water flow into the well. Without proper development, even a well drilled in a productive aquifer can underperform significantly.

The Water Well Journal recommends a comprehensive development programme that involves three main objectives: breaking down and removing drilling fluids from the aquifer, mechanically rearranging gravel pack and aquifer grains so that fines migrate into the well, and then pumping to remove accumulated sediment.

Common development techniques 🔗

Surging is one of the most widely used methods. It involves moving a tightly fitting plunger (surge block) up and down inside the well, creating pressure waves that push water alternately in and out through the screen. This action dislodges fine particles trapped behind the screen and brings them into the well for removal.

Airlift pumping uses compressed air injected into the well to lift water to the surface. When the air supply is turned off, the aerated water column falls back, creating a surging effect. This combination of lifting and surging is particularly effective for removing fine sediment.

High-velocity jetting directs pressurised water through the screen openings to break up any filter cake and flush out fines from the gravel pack. For best results, jetting is often combined with simultaneous pumping to carry loosened material to the surface.

Development should continue until the well produces clear, sand-free water at the desired yield. The process is typically monitored by measuring turbidity, sand content, and flow rate at regular intervals.

Step 8: Pumping test and yield assessment 🔗

Once development is complete, a pumping test (also known as an aquifer test) is conducted to determine the well’s sustainable yield, the aquifer’s transmissivity, and the drawdown characteristics. During this test, the well is pumped at a controlled rate for a specified duration – typically several hours to a full day – while water levels are measured at timed intervals.

The results help determine the correct pump size and installation depth, the safe pumping rate that won’t cause excessive drawdown, and the well’s long-term capacity. This is a critical step before finalising the pump installation and putting the tube well into regular service.

Step 9: Pump installation and platform construction 🔗

Based on the pumping test data, an appropriate pump is selected and installed. For agricultural tube wells, this is usually a submersible pump or a turbine pump, depending on the well depth and required discharge. The pump is set at a depth that ensures it remains submerged during operation while staying above the screen to avoid drawing in sediment.

A concrete platform or apron is constructed around the wellhead to prevent surface water from pooling near the casing and potentially contaminating the well. The wellhead should be properly sealed and capped when not in use.

Common challenges during tube well construction 🔗

Tube well construction doesn’t always go smoothly. Some of the common issues include encountering unstable formations that cause borehole collapse during drilling, hitting hard rock layers that slow progress considerably, or missing water-bearing fractures entirely – resulting in a dry borehole. In hard rock areas, finding fractures and fissures is especially difficult, and unsuccessful boreholes are not uncommon.

Other challenges include improper screen selection leading to sand pumping, inadequate well development that leaves drilling mud blocking the aquifer, and poor casing sealing that allows surface contaminants to reach the groundwater. Each of these problems can be minimised with careful planning, accurate well logging, and adherence to established construction standards.

Maintaining your tube well for the long term 🔗

A well-constructed tube well can serve reliably for 20 to 50 years or more, but only with regular maintenance. This includes periodic water quality testing, monitoring water levels to detect any declining trends, inspecting the wellhead and casing for damage, and cleaning or redeveloping the well if yield drops over time due to screen encrustation or aquifer clogging.

Keeping your original well log and construction records safe is equally important. These documents are essential reference materials whenever maintenance, rehabilitation, or pump replacement is needed.

What do you think? Have you considered how the geological conditions in your area might affect the choice of drilling method for a tube well? And what role do you think proper well development plays in the long-term performance of agricultural water supply systems?

References

1. https://www.slideshare.net/slideshow/tube-wells-and-their-design/63441854
2. https://www.epa.gov/sites/default/files/2016-01/documents/design_and_installation_of_monitoring_wells.pdf
3. https://wellowner.org/resources/basics/drilling-methods/cable-tool/
4. https://www.e-education.psu.edu/png301/node/903
5. https://www.sciencedirect.com/topics/engineering/percussion-drilling
6. https://www.ontario.ca/document/water-supply-wells-requirements-and-best-practices/constructing
7. https://roscoemoss.com/wp-content/uploads/publications/ggwc.pdf
8. https://www.lifewater.ca/drill_manual/Section_7.htm
9. https://waterwelljournal.com/the-well-development-process-2/