An open well usually refers to the most basic type of well, which is a cylindrical shaft dug into the ground using hand tools, with an opening that is not covered by a permanent cap. Open wells are almost always water table wells, meaning they are made just deep enough to reach the water table, allowing groundwater to fill the bottom of the well. This type of well commonly has a diameter of at least 3 or 4 feet (0.9-1.2 m), making it big enough for at least one person to stand in the well shaft while it's being constructed, and is usually no deeper than 200 feet (60 m). Open wells are common in developing countries because they are cheap and easy to dig. However, they can pose health hazards because of possible water contamination, and because animals and children can fall into the well and die from injury or drowning.
Many other types of wells require expensive boring or drilling, as well as the installation of pumps. An open well requires only hand tools and manual labor, and does not require a high level of technology to operate and maintain. However, if the ground is very hard or rocky, construction of an open well can be difficult or impossible. Also, these wells commonly access shallow groundwater that can be susceptible to contamination from various sources such as sewage, animal waste, and polluted runoff. This type of well is commonly lined with bricks, stones, concrete, or tiles to prevent the shaft from collapsing and to minimize the risk of contamination.
The water in these wells can be accessed by lowering a bucket on a rope or chain into the water. An open well submersible pump can also be installed to bring the water to the surface. There are various types of such pumps, including pumps powered by wind, gas or electrical power. Rope pumps or hand pumps are another alternative, especially in poor areas with few economic and technological resources.
The installation of cheap pumps, such as hand pumps or rope pumps, can increase the safety of the well, making it possible to access the water without leaving the well shaft open. This reduces the risk of water contamination and accidents. In many developing countries, other efforts are being made to make the wells safer. These efforts include recommendations and requirements that every open well be covered with a cap or lid, or fenced or walled in to prevent livestock, wild animals, and children from falling into the well shaft.