Well point water – reservoirs a few meters underground
Well point water use is a great bonus for parched gardens. Some gardens have a reservoir of water mere meters below the surface. For these home owners, a well point could be a useful source of water. Sinking a well point is not a complicated affair. There are numerous methods, each of which can be described as low technology. Well points are best sunk in sandy or lightly compacted soils. Rocky ground makes it difficult to dig a well point. In this case some form of drilling would be required. Drilling is expensive and not always possible. There are many gardens tucked away that have no access for drilling equipment. Well points on the other hand, do not require large and ungainly rigs. Well points usually make use of self-priming centrifugal pumps for abstraction. There is a depth restriction for this type of abstraction. Roughly 6m is the maximum depth from which a self-priming pump can draw. The theoretical maximum is 9.8 meters, but losses and inefficiencies lower this to around 6m. The self-priming centrifugal pump can pump to varying pressures. Typically, a household pump would deliver well point water at around 4 bar. A bar is the equivalent of 100 kPa. Another way to express pressure is in mm of mercury. At sea level, the atmosphearic pressure is 1 bar, which equates to 760mm of mercury.
Well point water quality is very dependent on geology and contamination. For instance, well point waters in the Southern Suburbs of Cape Town tend to exhibit a low pH and varying levels of iron. Well point water in the Philippi area tend to concentrations of nitrates which are attributable to farming activity. For those with well points on the West Coast, the ground water might taste a little salty.