Deep groundwater sampling requires more than simply choosing a pump with a high advertised maximum depth.
The actual performance of a groundwater sampling pump depends on water level, required sampling depth, pumping rate, tubing configuration, power supply and well conditions.
For deep monitoring wells, these factors should be evaluated before purchasing or deploying groundwater sampling equipment.
Why Is Deep-Well Groundwater Sampling Difficult?
As sampling depth increases, the pumping system must overcome a greater lifting requirement.
Deep wells can also create additional field challenges, including:
- Long tubing runs
- Higher lifting requirements
- Limited well diameter
- Difficult equipment installation
- Slow water discharge
- Remote field conditions
- Complex groundwater chemistry
A pump that works well in a shallow monitoring well may not provide the required performance at greater depth.
1. Start With the Actual Water Level
Do not select a deep-well pump based only on total well depth.
The important measurements include:
- Total well depth
- Static water level
- Required sampling depth
- Screen interval
- Expected drawdown
For example, a 200 m monitoring well does not necessarily require the pump to lift water from 200 m if the static groundwater level is substantially shallower.
2. Determine the Required Sampling Depth
The sampling depth may be different from the total well depth.
If the project requires a sample from a specific screen interval or groundwater layer, the equipment must reach that depth while maintaining the required pumping conditions.
3. Check the Required Flow Rate
Deep-well sampling does not automatically mean high-flow pumping.
The required flow rate depends on the sampling method.
Low-flow groundwater sampling generally requires controlled pumping, while well purging or well development may require substantially higher water output.
This is why a pump with an adjustable operating range can be useful for projects with multiple field requirements.
4. Check the Pump’s Lift Capability
Lift capability is one of the most important specifications for deep-well groundwater sampling.
However, the published maximum lift should be evaluated together with:
- Flow rate
- Tubing diameter
- Tubing length
- Power supply
- Groundwater conditions
- Pump configuration
Actual performance can differ from laboratory or nominal specifications.
5. Check the Well Diameter
A deep well may still have a relatively small internal diameter.
Before purchasing equipment, confirm:
- Pump diameter
- Cable dimensions
- Tubing dimensions
- Installation clearance
The equipment must be capable of reaching the required depth without interfering with the well casing.
6. Consider the Sampling Method
Different sampling methods require different pump characteristics.
Low-Flow Sampling
The system should provide stable and controlled flow.
Well Purging
Higher flow capacity may be required.
VOC Sampling
Equipment selection should focus on minimizing unnecessary disturbance and air exposure.
Multi-Purpose Field Work
If one pump is expected to perform both purging and sampling, a wider operating range can be advantageous.
AML918 for Deep-Well Groundwater Sampling
The AIMOLI AML918 is designed for groundwater sampling, well purging and well washing.
Published specifications include:
- Sampling flow: approximately 10–3000 mL/min
- Higher flow range: approximately 0.1–12 L/min
- Standard lift: 70 m
- Adjustable flow
- Meter-marked composite cable
AIMOLI reports that AML918 has been used in a groundwater sampling application at approximately 300 m depth.
This should be understood as a reported field application rather than a universal guarantee for every 300 m well.
For project-specific requirements, the well depth, static water level, flow rate and power configuration should be evaluated together.
See the AML918 groundwater sampling pump.
Groundwater Sampling Pump vs. Bladder Pump for Deep Wells
A groundwater sampling pump and bladder pump can both be used in deep wells, but the selection depends on the project objective.
A submersible groundwater sampling pump can be useful when both well purging and sampling are required.
A bladder pump can be considered when controlled low-flow sampling and reduced sample disturbance are the main priorities.
For projects involving VOCs, the sampling method and complete system configuration should be evaluated rather than choosing equipment based on depth alone.
See the AML919 groundwater bladder pump for a dedicated low-flow sampling option.
Deep-Well Groundwater Sampling Checklist
Before purchasing equipment, confirm:
- Total well depth
- Static water level
- Required sampling depth
- Well diameter
- Required flow rate
- Sampling method
- VOC requirement
- Tubing length
- Power supply
- Groundwater chemistry
- Required equipment materials
- Well purging requirements
Common Mistakes When Choosing Deep-Well Sampling Equipment
Mistake 1: Looking Only at Maximum Depth
A maximum depth number does not describe the complete pumping performance.
Mistake 2: Ignoring Flow Rate at Depth
The required flow rate should be considered together with lift capability.
Mistake 3: Ignoring Well Diameter
A pump must physically fit the monitoring well.
Mistake 4: Using the Same Method for Every Contaminant
VOC sampling and routine groundwater sampling can have different equipment requirements.
Mistake 5: Ignoring the Complete Sampling System
Pump, tubing, cable, power supply and field instruments all affect the final operation.
Conclusion
Selecting a groundwater sampling pump for deep wells requires a complete evaluation of depth, water level, flow rate, well diameter, sampling method and field conditions.
AML918 provides one option for projects that require both groundwater sampling and well purging, while AML919 provides a bladder-pump approach for controlled low-flow and VOC sampling.
For more equipment options, see AIMOLI’s groundwater sampling equipment category page.
