The Endress+Hauser Waterpilot series is designed for hydrostatic level measurement, particularly in freshwater, groundwater, drinking water, wastewater and saltwater applications. These submersible level probes are used in wells, boreholes, storage tanks, water towers, reservoirs, rivers, lakes and pumping stations.
Waterpilot transmitters determine liquid level by measuring the hydrostatic pressure generated by the liquid column. They are particularly useful when continuous level monitoring is required in applications where conventional top-mounted level instruments may not be the preferred solution.
Correct instrument selection is essential for measurement reliability, long-term stability and reduced maintenance requirements. Measuring range, probe diameter, cable length, liquid properties, materials and required approvals must all be considered.
The FMX11 and FMX21 serve different application requirements. The FMX11 is a compact probe intended primarily for freshwater, groundwater and drinking-water storage applications. The FMX21 offers a broader range of configurations for freshwater, wastewater and saltwater applications.
|
Technical feature |
Waterpilot FMX11 |
Waterpilot FMX21 |
|
Measuring principle |
Hydrostatic pressure |
Hydrostatic pressure |
|
Measuring cell |
Metallic measuring cell |
Oil-free capacitive ceramic measuring cell |
|
Pressure measuring range |
200 mbar–2 bar |
100 mbar–20 bar |
|
Maximum measurement distance |
20 m H₂O |
200 m H₂O |
|
Reference accuracy |
±0.35% for measuring ranges ≥400 mbar; ±0.50% below 400 mbar |
±0.2%; optional ±0.1% |
|
Output |
4–20 mA |
4–20 mA; optional/configuration-dependent HART |
|
Process temperature |
−10 to +70 °C |
Generally −10 to +70 °C; the 29 mm saltwater version has a different temperature limit |
|
Typical applications |
Freshwater, groundwater and drinking-water storage |
Drinking water, wastewater, saltwater and environmental monitoring |
|
Drinking-water approvals |
Available approvals depend on the selected version and market |
Available approvals depend on the selected version and market |
Technical note: These are published product-family specifications, not a guarantee that every value or option is available in every configuration. The current manufacturer documentation and complete order code should be checked before ordering. <Cite refs={["turn832655search0","turn832655search1","turn832655search2"]}/>
The FMX11 is a compact hydrostatic level probe with a metallic measuring cell. It is designed for freshwater, groundwater and drinking-water storage applications.
Typical applications include:
Small and medium-sized water storage tanks
Drinking-water reservoirs and water towers
Groundwater monitoring points
Wells and narrow boreholes
Dams, gauging stations, lakes and rivers
The FMX11 has a measuring cell range of 200 mbar to 2 bar and a maximum measurement distance of 20 m H₂O. Its reference accuracy is specified as ±0.35% for nominal measuring ranges of at least 400 mbar and ±0.50% below 400 mbar.
The manufacturer lists cable lengths from 6 to 30 m and a supply voltage of 8–28 V DC. Drinking-water approvals are available for applicable versions; the exact approval must be verified for the intended market and configuration. <Cite refs={["turn832655search0","turn832655search3"]}/>
The FMX21 is a robust hydrostatic level probe featuring an oil-free capacitive ceramic measuring cell. It is designed for applications requiring a wider measuring range and offers configurations for drinking water, wastewater and saltwater.
Typical applications include:
Deep wells and narrow boreholes
Water and wastewater process tanks
Reservoirs and environmental monitoring stations
Wastewater treatment plants
Saltwater applications and marine ballast-water tanks
The FMX21 supports measuring ranges from 100 mbar to 20 bar, with a maximum measurement distance of 200 m H₂O. Published reference accuracy is ±0.2%, with an optional ±0.1% version.
Depending on the selected configuration, the instrument supports 4–20 mA output with HART communication. An optional integrated Pt100 temperature sensor can provide simultaneous level and temperature measurement. The manufacturer also lists automatic density compensation as an available feature. These options must be verified against the selected configuration. <Cite refs={["turn832655search1","turn832655search2","turn832655search24"]}/>
The measuring cell is an important selection factor because it influences the instrument's suitability for the application.
FMX11 – metallic measuring cell
The FMX11 uses a metallic measuring cell and is intended for hydrostatic level measurement in freshwater, groundwater and drinking-water storage. Its compact design is useful for applications where the probe must fit into a narrow well or stilling tube.
FMX21 – capacitive ceramic measuring cell
The FMX21 uses an oil-free capacitive ceramic measuring cell. The manufacturer highlights its robust design, long-term stability and suitability for different water applications.
For FMX21, probe diameter and construction are also important. The manufacturer describes different versions for general freshwater applications, wastewater and saltwater. The 22 mm, 42 mm and 29 mm versions have different intended uses and material arrangements. The correct version should therefore be selected based on the liquid, installation dimensions and process requirements. <Cite refs={["turn832655search0","turn832655search1","turn832655search24"]}/>
Selecting a Waterpilot transmitter requires evaluating the measurement conditions as a complete system.
The measuring range must cover the maximum expected liquid level while providing sufficient resolution for the required operating range.
For initial selection:
FMX11: Consider applications within its specified range of up to 20 m H₂O.
FMX21: Consider applications requiring measurement distances of up to 200 m H₂O, subject to the selected configuration.
The maximum measurement distance is not the same as the maximum permissible process pressure. These parameters must be checked separately.
Hydrostatic pressure is related to liquid height and density:
[
p=\rho \cdot g \cdot h
]
Where:
p: Hydrostatic pressure
ρ: Liquid density
g: Gravitational acceleration
h: Liquid height
If the density differs from the assumed value, the calculated level may be affected. This is particularly relevant when liquid composition or temperature changes significantly. For suitable FMX21 configurations, automatic density compensation may be available; confirm the relevant option before specifying the instrument.
Probe diameter is especially important for narrow wells and boreholes. The available installation space, suspension arrangement and required cable length should be confirmed before selection.
The FMX21's different diameter variants also support different application requirements. The 22 mm version is intended for general freshwater applications, the 42 mm version for wastewater applications, and the 29 mm version for saltwater applications, subject to the manufacturer's stated limits.
The cable must be long enough to reach the required measurement point while allowing for the mounting arrangement and electrical connection.
Cable material must be compatible with the application and installation environment. The cable should not be selected based on length alone; the complete instrument configuration and environmental conditions must also be considered.
For freshwater, wastewater and saltwater applications, material compatibility is a key selection factor.
The FMX21 has different material arrangements depending on the probe version. The manufacturer lists stainless steel, ceramic, seals and polymer materials in relevant configurations. Do not assume that a version suitable for freshwater is automatically suitable for saltwater or chemically aggressive media.
The FMX11 uses a 4–20 mA output. The FMX21 is available with 4–20 mA and HART options, depending on configuration.
Confirm the following before ordering:
Required output signal
HART configuration requirements
Power supply and electrical connection
Compatibility with the PLC, RTU or monitoring system
Any requirement for simultaneous temperature measurement
Waterpilot instruments can be supplied with approvals for specific applications and markets. Depending on the model and configuration, these may include drinking-water approvals, explosion-protection certificates and marine approvals.
The exact certificate must be checked against the instrument's order code, the installation location and the applicable project requirements. A general statement about the Waterpilot series does not establish that every variant has every approval.
Waterpilot probes can be used for monitoring water levels in storage tanks, water towers, wells and reservoirs. For drinking-water applications, verify that the selected instrument version carries the approvals required by the relevant market and project.
The FMX21's wastewater-oriented version may be appropriate for selected wastewater treatment applications. Probe dimensions, material compatibility, installation conditions and the characteristics of the wastewater must be evaluated before specifying the instrument.
Submersible hydrostatic probes can support continuous groundwater-level monitoring in wells and boreholes. Cable length, measurement range, installation depth and the required measurement accuracy should be established from the monitoring plan.
Waterpilot instruments are used in environmental monitoring applications involving surface water. The selected probe must be suitable for the expected water conditions, installation arrangement and environmental exposure.
The FMX21 has a version intended for saltwater applications, including certain marine ballast-water tanks. Confirm the appropriate probe diameter, wetted materials, temperature limits and any required marine approvals before selection.
Correct installation is essential for reliable hydrostatic level measurement.
Mounting depth: Establish the intended measurement point and ensure the probe is installed according to the manufacturer's instructions.
Cable routing: Protect the cable from mechanical damage, excessive tension and unsuitable environmental exposure.
Pressure compensation: Where required by the design, ensure the pressure-compensation arrangement is installed and maintained according to the instrument manual.
Electrical connection: Verify the power supply, output signal, grounding and monitoring-system configuration.
Scaling: Confirm that the configured measuring range corresponds to the actual level range and the receiving system's engineering units.
Calibration and verification: Follow the manufacturer's instructions and the project's commissioning procedure.
Hazardous areas: If the installation is in a hazardous area, verify the applicable certificate, wiring arrangement and installation requirements.
The FMX11 and FMX21 should not be treated as direct equivalents simply because both measure level using hydrostatic pressure. Their measuring ranges, measuring cell technologies, accuracy specifications, materials, communication options and approvals differ.
Before replacing an existing Waterpilot instrument, compare:
Complete order code and nameplate information
Required measuring range and measurement depth
Probe diameter and mounting arrangement
Cable length and cable material
Measuring cell technology and accuracy requirements
Wetted materials and compatibility with the liquid
Output signal, HART requirements and power supply
Drinking-water, Ex or marine approvals
Any integrated temperature sensor or density-compensation requirements
Current product status and the availability of a suitable alternative
Important: A replacement decision must be based on technical equivalence, not model name alone. The new instrument must meet the application's measurement, mechanical, electrical and certification requirements.
For a Waterpilot quotation or replacement assessment, provide as much of the following information as possible:
Model and complete order code, if available
Photograph of the instrument nameplate
Required quantity
Maximum measurement depth or level range
Liquid type: freshwater, drinking water, wastewater or saltwater
Probe diameter and installation details
Required cable length
Output signal and communication requirements
Required certifications or approvals
Project country and delivery expectations
If the complete order code is unavailable, a nameplate photograph, technical specification or description of the existing installation can help establish the initial requirements. Any missing information should be identified before confirming technical equivalence.
The FMX11 is a compact probe with a metallic measuring cell, intended primarily for freshwater, groundwater and drinking-water storage applications. The FMX21 uses an oil-free capacitive ceramic measuring cell and offers a wider measuring range and configurations for freshwater, wastewater and saltwater applications. <Cite refs={["turn832655search0","turn832655search1"]}/>
The manufacturer's published specification lists a maximum measurement distance of 20 m H₂O for the FMX11. The actual selection must also account for the required measuring range and application conditions. <Cite refs={["turn832655search0","turn832655search3"]}/>
The FMX21 is offered in versions intended for freshwater, wastewater and saltwater applications. The correct version must be selected based on probe diameter, materials, temperature limits and the actual liquid conditions. <Cite refs={["turn832655search1","turn832655search24"]}/>
The FMX21 is available with 4–20 mA and 4–20 mA HART configurations. Confirm the communication option on the exact order code before ordering. <Cite refs={["turn832655search1","turn832655search2"]}/>
Not automatically. The instruments differ in measuring range, measuring cell technology, accuracy, available configurations and approvals. A replacement requires comparison of the complete order code and application requirements.
The Endress+Hauser Waterpilot series provides submersible hydrostatic level measurement solutions for water management and environmental applications.
The FMX11 is suited to selected freshwater, groundwater and drinking-water storage applications, with a maximum measurement distance of 20 m H₂O. The FMX21 offers a wider measuring range of up to 200 m H₂O and versions for freshwater, wastewater and saltwater applications.
Choosing the correct model requires more than comparing maximum measurement depth. Measuring range, probe diameter, cable length, materials, electrical configuration and required approvals must all be verified against the actual application.
Yeşil Grup Enerji is not an official distributor or authorized representative of Endress+Hauser. As an independent, brand-independent industrial supplier, we can support customers with:
Waterpilot model and complete order code verification
Technical specification and configuration checks
Legacy instrument and replacement research
Cross-reference and alternative-product assessment
Global sourcing research and RFQ management
Project-specific quotation support
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