Anatomy of a Borehole

What is a “borehole”?

Our friend and technical adviser, David Bell, has written a concise and easy-to-grasp explanation for all of you wondering “what exactly is a borehole? And how does it work?” Feel free to show off your new knowledge to friends at the next social gathering. Enjoy!
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FIGURE 1
Pump head assembly at top of well


Across Northern Uganda where ClearWater operates, borehole wells are the most reliable and secure source of clean water for people. These simple and inexpensive technologies have revolutionized the way people in developing countries access water.

Borehole wells allow people to tap into groundwater that is not accessible from the surface. as well as minimize the interaction of that water with surface pollutants by keeping it in a closed system until it reaches the tap.

Borehole hand pumps use human power and mechanical physics to move water in a one-way direction using a system of suction and discharge valves. The most common model of pump used in the region is the Mark II hand pump originally manufactured in India. A few of the major components of the Mark II are:

The Handle Assembly – This is a long lever, which is connected to a piston in the pump that draws water up to the tap. A longer hand lever can more efficiently draw water from a deeper well with fewer strokes.

The Water Tank Assembly – This houses many of the mechanical components of the well, including the pump-lever chain, upper connecting rods, and tap assembly.

Connecting Rods and Riser Pipe – These pieces usually come in 10 feet sections and are threaded with male and female ends to allow for variable well depths. Connecting rods are attached to the pump and drive the pistons, which draw water. Riser pipes are usually six-inch diameter pipes that convey water up to the tap.

Pump Cylinder – This is the main pump, which is set in the aquifer deep underground. The depth that a pump is set is based on the desired yield rates. A minimum yield of 1-2 cubic meters per hour is usually targeted. One cubic meter is equal to 264 gallons.


FIGURE 2
Pump cylinder at bottom of well

How boreholes break down:
Unfortunately hand pumps, like anything mechanical, tend to break down after improper use, neglect and just plain overuse. Long-term maintenance of rural water wells therefore has become the most challenging task for water aid groups. Which is why Clearwater contractors work with recipients to educate them to proper maintenance schedules.

Common mechanical well problems include:
• Broken handle assembly that is no longer properly connected to the chain and connecting rods
• Loose mechanical components in water tank assembly
• Loss of suction in the pump
• Riser pipes become corroded and dislodged
• Cracked pedestal and well riser, which can create unsanitary conditions inside the well

How boreholes can be maintained:
Ideally a well is regularly checked and maintained by a trained pump operator, whose duties are to make sure major breakdowns do not occur, which could severely interrupt service.

A typical schedule of maintenance could involve the following:

Daily
Monitor pump operation
Maintain pump and area cleanliness
Maintain drainage of wastewater
Educate users on proper pump use and receive comments

Weekly
Lubricate moving parts
Check tightness of nuts and bolts
Check security of pump on pedestal

Monthly
Check output rate
Check for condition of concrete apron

Yearly
Raise pump cylinder from well for inspection and replace parts where necessary
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