There are typically two types of wells that the Angus Home Inspector encounters; the shallow well and the deep well.
Shallow Well
The Shallow Well is easily identified by the pump being located above ground, usually in the house. When the pump is located above ground the maximum lift that a pump has is 30 feet when conditions are perfect. Usually 26 or 27 feet of depth is the most that a jet or piston pump can draw water from. A well is considered to be shallow if it is less than 50 feet deep. The source of a well is an aquifer. An aquifer is an underground layer of permeable soil (such as sand or gravel) that contains water and allows the passage of water. Aquifers are replenished as rainfall seeps down through the soil. Ground water travels through permeable soil on top of hard or impermeable layers. Shallow wells usually are only deep enough to intercept the uppermost (or most easily reached) perched water table.
Since shallow wells penetrate into aquifers that are near the ground surface, they can become contaminated by barnyards, pastures, sewers, chemicals, or septic tank systems. Both rainfall and surface water runoff can carry pollutants down into shallow aquifers and well water. Since a hole penetrating an aquifer provides a direct route for contamination, wells must be designed to prevent pollution from entering and contaminating ground water.
Deep Well
Deep Wells will have the pump located at or near the bottom of the drilled well. There is no limit to how far you can pump water unlike the shallow well which is limited to a depth of approximately 27 feet. Deep or confined wells are sunk through an impermeable stratum into an aquifer that is sandwiched between two impermeable strata (aquitards or aquicludes). The majority of deep aquifers are classified as artesian because the hydraulic head in a confined well is higher than the level of the top of the aquifer. If the hydraulic head in a confined well is higher than the land surface it is a “flowing” artesian well.
For information on who installed your well check the top of the well cap. Most well installers put their Company Name and Phone Number on the cap.
Testing Your Wells Water Supply
Well water flow is measured directly at the well tank or a faucet as close as possible to the tank. Flow is reported in gallons per minute (GPM) and pressure in pounds per square inch (PSI). Flow is measured with a calibrated flow meter. When the test is conducted at a faucet other than at the well tank, results may be lower than the actual well flow. Water flows through piping and valves between the well tank and faucet that create a pressure drop. This reduces the measured flow rate at the test faucet. If water flows through a water treatment system or filter, additional pressure drops are present. We try to measure flow directly at the well tank. This information is provided to make you aware of the accuracy of this test.
Pumping Test
A pumping test is a practical, reliable method of estimating well performance, well yield, the zone of influence of the well and aquifer characteristics (i .e ., the aquifer’s ability to store and transmit water, aquifer extent, presence of boundary conditions and possible hydraulic connection to surface water) . A pumping test consists of pumping groundwater from a well, usually at a constant rate, and measuring water levels in the pumped well and any nearby wells (observation wells) or surface water bodies during and after pumping.
Wells can be pump tested solely to provide a greater confidence in the driller’s estimated well yield . These tests are typically shorter in duration (e .g ., 4 to 12 hours) and are
commonly done on domestic or single-residence wells.