Recent experience helping a group of young engineering students in a Florida chapter of Engineers Without Borders with their Dominican Republic project led me include a brief introduction to water wells here.
Discussion of the well seal, sand and gravel is a good idea before proceeding to a discussion of pump installation.
Perforations in the casing allow water to enter into the well casing and then become available to the pump. One little hole will only allow a small amount of water to flow out of a leaking bucket, the same concept applies to the perforations allowing water to enter the well casing. More and larger holes will allow more water to enter.
An open hole refers to a well that has no well casing, this is possible in formations that do not erode and bring material into the well or cause the bore hole to collapse. The other extreme is a well that includes a water bearing strata made up of extremely fine sand particles that tend to flow into the well casing with incoming water. The fine sand example requires many small perforations or slots for water to enter, rather than fewer large openings. The size of the casing perforations is chosen so that sand placed around the well casing cannot enter the perforations yet has interstices between the sand particles to catch the native sand formation that attempts to flow into the well with incoming water. The point here is that there is a relationship between the water bearing strata geology, the sand or gravel particle size filling in around the casing and the size and quantity of casing perforations.
A small derrick made of 2" water pipe slipped into a 2.5" or larger stand pipe. The strength is sufficient for small pumps and 10 foot (3 meter) lengths of drop pipe. Small lift derricks are easily moved from well to well. Each well requires a simple derrick mount, to receive the derrick. The top piece that holds the pulley also has a piece of 2.5 inch pipe that slips over the vertical tall pipe. This system requires very little fabrication effort and provides independence from expensive machinery for minor well maintenance. The top of the derrick should be about 13 feet ± above the top of the well casing (3.65 M). Total length of derrick stand pipe to provide sufficent space for pully, hook, bale, ten foot pipe joint (3 M) and length from top of casing to bottom of mount is a minimum of 19.7' = 6 Meters. Use a full length of pipe and cut it shorter with experience.
The easiest method for a single person to place a 20 foot (6 M) length of pipe into the mounting pipe is to stand fairly high on a stable ten foot ladder (3 M). It is not overly cautious to brace the ladder with tight wires for this procedure. Two people working together can install the derrick quite easily.
The hand crank used to lift the pump can be made from one used on a boat trailer to pull a boat from the water onto the trailer. Use a ratchet mechanism which does not allow the handle to spin free if you accidentally let go. Dropping the pump or any tool into a well necessitates what is known as a fishing expedition, one must go through a sometimes tedious and intellectually challenging effort to retrieve the object that has been dropped. Complicating matters is the possibility the pump and wire moving at high velocity may become stuck.
A falling pump presents added danger from the electric line and the rope attached to it. One can be injured should either of these wrap around a wrist, ankle or neck. Do not attempt to grab ropes or electric lines and stop a falling pump!
The bale threads onto the pipe sections so that the hook can be inserted in order to lift or lower the pump. This is a necessary tool which is easily made by welding a piece of rebar to a pipe connector of the proper size.
Both professional bale and hook includes swivels. If the hook and bale do not have swivel mechanisms, spin the hanging pipe joint backward before connecting.
The slip sits on top of the well casing, it supports the weight of the pump and water filled pipe above the water line as pipe joints are removed or added. The lift line is temporarily disconnected at this time, care and concentration keep the pump from slipping off the slip and falling to the bottom of the well, retrieving lost items from the bottom of the well is called fishing. Small bumps welded on both sides of the slip's U shaped slot help keep the pipe connector in place.
Some slips have elaborate safety chains which hold the drop pipe firmly in the slip. Much thought and energy has gone into devising safety clamps for slips. A short length of rope around the pipe under the slip and then over the slip will help hold the drop pipe in the slip yet still leave room while using wrenches to work with pipe and joints, some people also attach small safety ropes to the wrenches.
Threaded connectors are commonly used with steel or heavy wall plastic pipe. The slip functions the same with threaded pipe and couplers or if threaded male and female couplings are glued to the pipe. Allow glue to cure for several hours before setting pump. Be wary that a threaded pipe may snap where it enters the coupler if the pipe is bent with too much force if a strong crew struggles while lifting the pump without a derrick. Secure the lift line before working with threaded joints of any type.
The solid horizontal line represents the starting direction of a horizontal well bore hole, its associated broken line indicates a probable path as the drill bit is pulled downward by gravity. The vertical well path tends to drift downhill as the bit slides off hard spots large and small. The oval represents an exposed cliff side that shows a peach-like blush of moisture during the rainy season. The small broken line represents a road from which one might have seen the subtle damp oval, perhaps waiting over years to check again and finally realize the full meaning.
Imagine yourself in California with west to the right, direction of continental scale subterranean water flow will very likely be from lower right toward upper left. This occurs because water flowing from the left is from the continent, it encounters impermeable strata and is forced downward until it finds a route upward and out to the sea. Seasonal water flows from local rain travel from upper left toward lower right. Such an up and down zig-zag path may happen many times as continental water travels seaward, sometimes the water will appear as running on the surface or simply as the blush on a rock cut face as illustrated. Vertical and horizontal wells in the same strata will yield a similar amount of continental water during a dry summer if the vertical well is artesian because its water origin is from a higher continental divide.
The point here is that looking for water can be quite successful with nothing more than educated and intelligent observation.