Flow rate is the quantity of water obtained per unit time, for example litres per minute or cubic metres per hour. Source capability and the maximum capacity stated on a pump box are not the same. A pump may be able to move more water than enters the water needle at an acceptable water level.
Water level may fall during pumping and recover when pumping stops. Long-term operation can also be affected by neighbouring sources and seasonal conditions. The assessment therefore considers flow and its relationship with water level and time. T02
What does a simple container test show?
Calculation example. If a 10-litre container fills in 30 seconds, flow is calculated as follows:
Q = 10 × 60 / 30 = 20 l/min = 1,2 m³/h.
This figure shows the flow at that moment and measurement point. It does not prove the source will supply the same amount for two hours or in the driest season. If measured from a system with a filled tank, initial flow may include stored water, so the test arrangement must be clear.
To compare repeated measurements, do not change conditions without recording them: hose length, pump mode, open taps or tank state. Otherwise, different figures may indicate a different test procedure rather than a change in the source.
What should a more thorough test record?
The test record should include the date, duration, pump, flow, initial and operating water levels, reference point and recovery observations. Sand, air, marked cloudiness or supply interruptions should also be noted.
This article does not set one mandatory test duration for every construction. The responsible specialist selects the programme according to its purpose and applicable procedures. Customers can reasonably ask for the information to be retained rather than just being told water flows.
Why is the source developed first?
Fine particles may remain around the screen and in the water after installation. Development prepares the intake zone for operation and removes material introduced during installation. It is not a promise to create a high-yield source in any ground. The test result should reflect a prepared construction, not just its first startup.
Even a good one-day test does not remove seasonal uncertainty. Groundwater levels may decline during drought, making local conditions and available observation history important. T07
How does yield compare with demand?
An illustrative example: if a 10 l/min shower and a 12 l/min irrigation zone are planned to run together, demand at that moment is 22 l/min. This is not a typical standard for every home; actual fixture flow rates need to come from their data or measurements.
If source capability is lower, first consider separating uses in time, sensible irrigation zoning or a justified storage solution. A larger pump alone cannot fill a missing water balance. Selection starts with what the source can reliably provide and ends with how that water can be used conveniently.
Information sources
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- T02
- T07
Sources checked on 2026-09-30. If the manufacturer has changed the product or documentation, follow the latest technical information for the specific model.