What the pumping test screening worksheet does
A pumping test sheet can look complete and still be unusable. Clocks roll over at midnight, the measuring point changes when a pipe is removed, flow is read from a bucket at one time and a meter at another, and missing readings are quietly filled in. If those faults go unnoticed, the drawdown curve, the estimated yield and the pump selection built on it can all be wrong.
The worksheet above checks the record before interpretation. It:
- Fixes the identity of the well, the test and each instrument
- Keeps the original readings untouched and records every correction separately
- Reconciles clock time, elapsed time and the measuring point
- Splits the test into its actual phases: pre-test, pumping steps, interruptions and recovery
- Checks that discharge and water level behave consistently
- Issues a purpose-specific result: fit for a volume check, fit for drawdown analysis, or not yet usable
It does not calculate aquifer properties, declare a sustainable yield or give permission to pump. Those decisions belong to the hydrogeologist or the responsible engineer, using screened data.
Why borewell test data goes wrong
Field conditions in Telangana and Andhra Pradesh are demanding: tests run through the night, readings are taken by hand in heat and dust, generators stop, and crews change. Common faults are predictable:
| Fault | How it appears in the data | Screening check |
|---|---|---|
| Midnight rollover | Elapsed time jumps backwards or a reading appears 24 hours early | Rebuild elapsed time from date plus clock time |
| Changed measuring point | Sudden step in water level with no change in pumping | Confirm reference: top of casing, ground level or a marked point; apply the stick-up difference |
| Unit mix-up | Flow jumps by a factor such as 3.6, 4.5 or 60 | Check whether litres per minute, m³/h or gallons per hour were recorded |
| Pump stop not recorded | Water level rises during “pumping” | Compare with generator or pump log; mark as interruption |
| Missing readings filled in | Suspiciously smooth or repeated values | Flag as estimated; exclude from analysis that needs measured data |
| Recovery timed from the wrong origin | Recovery curve that does not start at the stop level | Record exact pump stop time; compute time since stop and time since start |
Step-by-step screening method
- Identify the record. Well identity, location, date, test type (constant-rate, step or recovery only), pump setting depth and the people who took readings.
- Preserve the original. Scan or photograph field sheets and keep logger files unchanged. All work is done on a copy.
- Fix the geometry. Record the measuring point, its height above ground, the casing and pipe arrangement and the depth to the pump intake.
- Rebuild time. Combine date and clock time into one timestamp, correct any logger offset, and compute elapsed time from pump start.
- Segment the test. Mark the static level period, each pumping step, any interruption and the recovery, using the actual event times.
- Normalise units. Convert water levels to metres from the same reference and discharge to a single unit, keeping the original value alongside.
- Calculate drawdown. Drawdown = pumping water level − static water level, both measured from the same point.
- Check discharge stability. Compare flow readings within each step with the tolerance the test plan sets.
- Flag every exception. Missing, estimated, doubtful and corrected readings each get their own code.
- Issue the disposition. State which analyses the data supports, over which interval, and what remains unresolved.
Units and conversions used in Indian borewell work
Borewell yields are quoted in many ways across India, and confusion between them is common. The worksheet keeps the original unit and converts to a single working unit.
| Unit as recorded | Conversion | Note |
|---|---|---|
| Litres per minute (L/min) | 1 m³/h = 16.67 L/min | Common for bucket-and-stopwatch readings |
| Litres per second (L/s) | 1 L/s = 3.6 m³/h | Used in many engineering reports |
| Imperial gallons per hour (gph) | 1,000 gph ≈ 4.55 m³/h | Widely used by drillers in South India; confirm imperial, not US |
| US gallons per minute (gpm) | 1 gpm ≈ 0.227 m³/h | Appears on imported pump data |
| Feet of water level | 1 ft = 0.3048 m | Older sheets and some loggers |
Discharge and water level must tell the same story
A drawdown record only means something if the discharge was known and reasonably steady. Screening checks:
- How was flow measured? Bucket and stopwatch, V-notch or orifice, or a flow meter. Each has its own accuracy and its own failure modes, such as air in a meter or a bucket too small for the flow.
- Was it steady? A constant-rate test should stay within the tolerance set in the test plan. If the rate drifted down as the pump lost head, the drawdown curve reflects that drift, not just the aquifer.
- Do events line up? A rise in water level should match a drop in flow or a pump stop. If it does not, the level reading or the flow reading is suspect.
- Is the volume plausible? Total volume pumped, from flow and time, should agree with any tank or meter totaliser.
Screening the recovery
Recovery data, taken after the pump stops, is often the most reliable part of a test because it is free of pump-rate fluctuations. It is also easy to spoil.
- Record the exact stop time. Recovery analysis needs both time since pumping started and time since it stopped.
- Residual drawdown = water level during recovery − static level.
- Ratio methods that use time since start divided by time since stop cannot use the reading taken at the instant of stopping, because the ratio is undefined there. Flag that point rather than forcing a value.
- Check for backflow from the rising main when a foot valve or check valve leaks; it can make early recovery look faster than it is.
Worked examples
Example A: midnight rollover and a changed measuring point
A test starts at 21:00. Readings after midnight are recorded as 00:15, 00:30 and so on, and a spreadsheet computes negative elapsed times. Rebuilding timestamps from the date fixes the sequence. At 02:00 the level suddenly appears 0.6 m shallower with no change in flow. The crew notes show the reference moved from the casing top to ground level when a flange was removed. Applying the 0.6 m stick-up difference removes the false step. Both corrections are recorded, with the original values kept.
Example B: an interruption hidden in the average
A constant-rate test reports an average of 9,000 L/h. The generator log shows a 25-minute stop at hour five, during which the water level recovered. The average flow is therefore misleading, and the drawdown after restart is not a continuation of the earlier curve. The worksheet splits the test into two pumping periods and limits analysis to the first, unless the hydrogeologist chooses a method that handles the interruption.
Example C: a high acceptance rate hides a critical gap
Of 120 readings, 112 pass screening, which looks good. But the eight that fail are the first eight minutes of pumping, the period needed for early-time analysis. The record is suitable for a late-time and volume check, but not for early-time drawdown interpretation. The disposition says exactly that, rather than giving a single overall score.
Where compressors fit: development and airlift testing
Many borewells in hard-rock areas of Telangana and Andhra Pradesh are developed and airlift-tested with the drilling compressor before a submersible pump is installed. Airlift yields are useful field indications, but they are not the same as a controlled pumping test: discharge is mixed air and water, flow can surge, and the submergence of the air line affects results. Screen airlift records with the same care, and label them as airlift data so they are not confused with pumped-test results. The borewell yield testing and production duty page explains the difference in more detail.
How Reddy Compressors helps
We supply all types, all brands and all models of borewell compressors: new machines, used and refurbished units, rentals, service and spare parts. That includes high-pressure units for DTH drilling at 600–1,500 cfm and 200–400 psig (13.8–27.6 bar), and special units up to 35 bar (507.6 psig). We work with machines from ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and others as an independent multi-brand specialist, not an authorised dealer. We have tie-ups with all major and reputed brands. For development and airlift work, we can advise on compressor pressure and flow for the depth and submergence involved. Aquifer interpretation and yield certification remain with the hydrogeologist.
Our office is at Tarnaka, Secunderabad. Service teams cover Telangana and Andhra Pradesh, and compressors, rentals and spares are supplied to rig owners and drilling contractors across India.
What to send us
- Borewell depth, diameter and the compressor currently used on the rig
- The drilling, development or airlift duty you need air for
- Compressor make, model, serial number and a nameplate photograph for service or spares
- Site location and access for delivery of rental machines
- The fault or performance issue, if the compressor is not delivering as expected
Frequently asked questions
How do I calculate drawdown in a borewell pumping test?
Drawdown is the pumping water level minus the static water level, with both measured from the same reference point, such as the top of the casing. Measure the static level before the pump starts and allow it to settle. If the measuring point changes during the test, correct all readings to one reference and record the correction, otherwise the drawdown will show a false step.
What is the difference between an airlift yield and a pumping test?
An airlift yield is measured while the drilling compressor blows water out of the borewell, so the discharge is mixed with air and can surge. It is a quick field indication. A pumping test uses a pump at a controlled, measured rate with water levels recorded over time and during recovery. Pumping test data is the basis for proper yield assessment and pump selection.
How long should a borewell pumping test run?
The duration depends on the purpose of the test, the expected use of the well and the method the hydrogeologist intends to apply. A short test may be enough for a domestic well, while a supply well for irrigation, industry or a water scheme usually needs a longer constant-rate test followed by recovery. Agree the duration and readings schedule before the test begins.
How do I convert gallons per hour to litres per minute?
Borewell yields in South India are often quoted in imperial gallons per hour. One imperial gallon is about 4.546 litres, so divide gallons per hour by 60 and multiply by 4.546 to get litres per minute. For example, 1,000 gph is about 76 L/min, or about 4.55 m³/h. Confirm whether the figure is imperial or US gallons, because US gallons are smaller.
Why does the water level rise during a pumping test?
A rise during pumping usually means the pump rate fell or the pump stopped briefly, for example when a generator tripped or a valve was adjusted. It can also come from a changed measuring point or a misread tape. Check the pump and generator logs and the flow readings for the same time. If no cause is found, flag the readings rather than removing them.
What compressor do I need for borewell development and airlift?
It depends on borewell depth, the depth of the air line below the water level and the diameter of the well. Deeper wells and greater submergence need higher pressure; larger diameters and higher yields need more flow. Borewell compressors typically range from 600 to 1,500 cfm at 200–400 psig. Send us the depth, diameter and expected water level and we will advise on a suitable machine.
Related pages
Calculators and worked examples
These tools give indicative figures for screening, comparison and for preparing an enquiry. They run in your browser and send nothing. No prices or tariffs are assumed: enter your own to see costs. Efficiencies and other figures shown are example values: replace them with your own. Results are not a performance guarantee or a design certificate; final selection is confirmed by a service engineer against the machine data sheet and the site.
Pumping-test discharge stability and volume check
Screen the discharge readings for one pumping step: convert them to one unit, check they stayed within the test plan’s tolerance, look for unit mix-ups, and compare the pumped volume with the totaliser or tank.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Discharge readings during the step, in time order: 152, 150, 149, 151, 148, 150, 147, 146
- Unit of the readings: litres per minute
- Allowed deviation from the mean in the test plan (%): 5
- Elapsed time of the step (h): 8
- Time the pump was stopped within the step (min): 0
- Volume from totaliser or tank for the step (m³; 0 = not available): 70
Result
- Mean discharge: 8.95 m³/h = 149.1 L/min = 2.49 L/s
- Lowest and highest reading: 8.76 to 9.12 m³/h
- Largest deviation from the mean: 2.1 % (within the 5% tolerance)
- Drift, first to last reading: -3.9 %
- Hours actually pumping: 8 h
- Volume from readings: 71.6 m³
- Against totaliser or tank: +2.3 % (1.6 m³)
- Screening result: Fit for a volume check and for drawdown screening (hydrogeologist to interpret)
Method. Each reading is converted to m³/h (1 L/min = 0.06 m³/h; 1 L/s = 3.6 m³/h; 1 imperial gallon = 4.54609 L; 1 US gallon = 3.78541 L). Mean = average of the readings. Deviation = (reading − mean) ÷ mean. Drift = (last − first) ÷ first. Volume = mean rate × hours actually pumping (elapsed time − stops). A reading that differs from the median by a factor near 3.6, 4.5, 16.7 or 60 is flagged as a possible unit mix-up. Screening result: not yet usable for drawdown analysis if the discharge is outside tolerance, a reading is zero, a unit mix-up is flagged or the pump stopped within the step; fit for a volume check when the totaliser or tank agrees within the tolerance. Screening only: aquifer properties and yield are for the hydrogeologist.
What to take from it. An average that includes a pump stop is not a pumping rate. Split the test at every interruption.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.
Drawdown with a measuring-point correction
Calculate drawdown from a static level and a series of pumping water levels, correcting readings taken after the measuring point changed (for example from casing top to ground level) and flagging rises during pumping.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Levels recorded in: metres
- Static water level below the original measuring point (m or ft, as selected): 12.4
- Pumping water levels in time order, below the measuring point in use at the time (m or ft): 15.2, 16.1, 16.6, 16.9, 16.4, 16.5, 16.6
- Reading number from which levels were taken from ground level (0 = no change): 5
- Stick-up: height of the original measuring point above ground (m or ft; used only if a reading number above is entered): 0.6
- Rise between readings that counts as a step (m): 0.2
Result
- Correction applied: +0.6 m to readings 5 to 7 (ground level converted to the original measuring point)
- Final pumping water level: 17.2 m below the original measuring point
- Final drawdown: 4.8 m
- Maximum drawdown: 4.8 m
- Drawdowns after correction: 2.8, 3.7, 4.2, 4.5, 4.6, 4.7, 4.8 m
- Steps (rises) in the uncorrected data: at reading 5
- Steps remaining after correction: none
Method. All levels are depths below the original measuring point (casing top). A level read from ground level is converted by adding the stick-up (height of the casing top above ground). Drawdown = pumping water level − static water level, both from the same point. A drawdown that falls by more than the step threshold between two readings is flagged: during constant-rate pumping the level should not rise, so check for a pump stop, a flow change or a misread tape. Original readings are kept; the correction is shown separately.
What to take from it. A sudden shallower reading with no change in pumping is usually a changed measuring point or a pump stop, not the aquifer. Record the correction; do not delete the reading.