Test results should become a part of the permanent records. You should not modify the precision and accuracy of the measurements taken. You may modify the above procedure depending on well requirements and local site conditions. Conduct another reading schedule until the pumping level stabilizes. When the drawdown stabilizes, increase the pumping rate to produce the maximum drawdown or about 90 percent of the maximum capacity of the pump. Try to follow the above reading schedule, starting from the time the flow rate was increased. Repeat the measurements, noting the exact time that the new flow rate was started.Do not stop the pump between these test segments. After the drawdown stabilizes (1 to 4 hours), the pumping rate should increase to a new, constant flow rate, which will produce two-thirds of the capacity of the pump. You must record the exact time of each reading (not the intended or scheduled time). Establish the desired, constant flow rate quickly.The recommended schedule is as follows: 0 (at the start of the test) 30 seconds, 1 minute, 2 minutes, 4 minutes, 8 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, and so forth. A reading schedule that doubles the time between readings is preferable. Initially, take readings rapidly, and then spread out the readings as the test continues. Record the flow rate, drawdown, and testing time.Continue pumping at a constant flow rate until the drawdown remains constant (about 1 to 4 hours).Monitor and adjust the flow rate early in the test because as the drawdown increases the flow rate decreases.Pump at a rate that will lower the water in the well about one-third of the maximum drawdown possible (one-third the distance from the static water level to the top of the well screen) or about one-third of the rated capacity of the pump.Measure the static water level in the well before testing, and measure the drawdown during the test. If the well will be a permanent installation and maintained in the future, you should conduct a detailed test. You should use two different testing procedures when a pump is available, depending on the intended use of the well and the available testing time. Accurately measuring drawdown is not possible during the test because the water level constantly fluctuates.Ī.
4 HOUR WELL DRAWDOWN TEST FULL
You must know the bailer's volume and count the number of times per minute the bailer is brought up full to estimate the GPM of the well. You can estimate the yield of a small well by bailing water from the well rapidly if no pump is available. This test will determine the specific capacity of the well. If you use a temporary unit, it must be adequate to draw down the water and hold it at a prescribed flow rate for a period of hours. You will normally use the permanent pump for pump testing. Chapter 8 Well-Performance Testing ProceduresĨ-1.
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