Drinking Water Network Monitoring: An IoT Guide for French Municipalities 2026

July 3, 2026 · 13 min read

13 min read

IoT Infrastructure

Modernizing the remote management of drinking water networks has become a priority for French local governments. Faced with increasing regulatory requirements (self-monitoring, NIS2, GDPR), aging remote monitoring equipment from the 2000s, and the performance requirements of public service delegation contracts, water utilities must rethink their monitoring architecture.

This practical guide is intended for technical managers, water and wastewater directors, and chief information officers (CIOs) at local government entities—water districts, municipal utilities, and intermunicipal associations—that oversee drinking water systems.

Current Status: The Water Remote Management Infrastructure in France

An Aging Fleet

Remote management of drinking water networks in France currently relies heavily on equipment installed between 2000 and 2015. The dominant technologies are:

SOFREL S4W/S500 Modems: Deployed on a large scale by concession operators (Veolia, Suez, Saur) across water networks, these GSM/GPRS modems use the 2G/EDGE network, which is currently being phased out
Servelec RTUs (formerly Sontay) and Lacroix Sofrel: a range of RTUs designed specifically for water systems, used at pumping and treatment plants
Concessionaires’ proprietary systems: Each concession operator has deployed its own infrastructure (Veolia Hub Eau, Suez IntelliO) using proprietary protocols that limit the ability to take over operations directly

The 2G Shutdown: A Catalyst for Modernization

Orange has officially announced that it will shut down its 2G network in 2026 (after several delays). SFR has already shut down its 2G network in several areas. Bouygues Telecom is following the same path.

SOFREL S4W modems and other 2G/GPRS RTUs used at water towers, pumping stations, and lift stations will no longer work after these shutdowns.

This is a major opportunity to modernize by transitioning to 4G LTE solutions with a centralized cloud-based monitoring platform.

Modern Monitoring Architecture for a Drinking Water Network

Typical Sites to Monitor

Site Type	Key Parameters	Field Equipment
Pumping station	Discharge flow rate, pressure, tank level, operating hours, power consumption	Schneider M340 or Siemens S7-1200 PLC, 4-20 mA sensors
Water tower / reservoir	Water level, inlet/outlet pressure, fill valve	Ultrasonic or pressure level sensor, Modbus flow meter
Treatment plant	Turbidity, residual chlorine, pH, conductivity, temperature, treated flow rate	YSI, Hach, and WTW multiparameter sensors via Modbus RS-485
Booster station	Downstream pressure, flow rate, pump status, motor faults	Modbus variable frequency drives, local PLC
Utility meter	Flow rate, meter reading, nighttime leak detection	MID-compliant meter with pulse or Modbus output

Recommended Architecture

Migration from Existing Systems

Replacing a SOFREL S4W Modem

The SOFREL S4W is the most widely used modem on French water networks. The migration to the Eziwan Gateway is designed to be non-invasive.

Migration Steps:

Preliminary Audit (1 hour remotely): identification of the Modbus registers configured on the S4W, mapping of the I/O used (digital inputs, analog inputs, relay outputs), list of current SMS recipients
Delivery of the pre-configured Gateway: The Eziwan Gateway is delivered with your configuration template (Modbus registers identical to those on the S4W, same alarm thresholds, same SMS recipients)
Physical Replacement (30–45 minutes per site): The Gateway connects to the same RS-485 wiring. The 4G SIM card is inserted and activated. The cloud connection is established automatically
Verification: An Eziwan technician takes remote control to validate data transmission and alerts
Commissioning: The site appears in the cloud dashboard with all its historical data (starting from the migration—S4W historical data is not transferred)

Compatibility: The Eziwan Gateway reads all Modbus registers configured on your PLC (Schneider M340, Siemens S7-1200, Lacroix E30, etc.). The migration does not require any modifications to the field PLC.

Migration Cost: The Eziwan Gateway is less expensive than a new SOFREL S4W and offers expanded features (VPN, multi-protocol support, OTA). For a fleet of 50 stations, the return on investment compared to purchasing new S4W units is immediate.

Migration from a delegated system (end of DSP)

When a project is brought back under direct municipal management or there is a change in the contractor, the local government often loses access to the outgoing operator’s proprietary monitoring system. The transition can result in weeks or months without centralized monitoring.

Eziwan's Approach to DSP Transitions:

Early deployment: Install the Eziwan gateways 3–6 months before the end of the DSP contract, running in parallel with the existing system
Parallel validation: Compare Eziwan data with data from the outgoing operator to verify consistency
Smooth transition: By the end of the DSP contract, the Eziwan monitoring system is already operational and validated
Historical data continuity: 3–6 months of historical data are already available on the Eziwan platform

Regulatory Compliance

Self-Monitoring and ARS Requirements

The decree of July 21, 2015, amending the decree of May 2, 2007, imposes self-monitoring requirements on wastewater treatment plants (WWTPs) and drinking water production units (DWPUs):

Parameters to Monitor and Log (UPEP):

Treated water flow rate (m³/h and m³/day)
Turbidity of treated water (NTU) — alert threshold: > 1 NTU
Residual chlorine content (mg/L) — alert threshold: < 0.1 mg/L
pH (6.5 to 9.0)
Conductivity (μS/cm)
Temperature (°C)

Archiving Requirements:

Minimum retention period of 5 years
Certified UTC timestamp
SANDRE-compatible export format for transmission to government agencies
Access available to DDETSPP (formerly DDASS) upon request

How Eziwan Meets These Requirements:

Minimum 10-year data retention (beyond the regulatory 5-year requirement)
UTC timestamps on each measurement, digitally signed
CSV and JSON exports in SANDRE format
API access for regulatory agencies
Configurable automatic daily and weekly reports

NIS2 Directive: Applicability to Drinking Water

The transposition of the NIS2 Directive into French law (Law of April 16, 2024) classifies water operators into categories based on their size:

Key Entities:

Drinking water operators serving > 50,000 people OR
Revenue > 50 M€ OR
Designated as OIV (Operators of Vital Importance)

Significant Entities:

Drinking water utilities serving more than 10,000 people OR
Revenue greater than 10 M€

NIS2 requirements relevant to remote water management:

Requirement	Requirement	How Eziwan Meets It
OT/IT network segmentation	OT gateway isolated from the office network	Gateway operates in the OT zone; no incoming traffic
Remote access control	MFA + logging	OpenVPN/IPSec VPN + MFA + full session log
Vulnerability management	Patch management	Automatic OTA firmware updates for the gateway
Incident notification	< 24 hours to ANSSI	Exportable incident log, documented procedure
Subcontracting chain	Vendor audit	Eziwan ISO 27001 certified, hosting in France, GDPR compliant

Case Study: Water District with 80 Stations

Background: An intermunicipal association manages 80 pumping stations (12 to 350 m³/h) and 6 water towers across a rural area comprising 45 municipalities. Existing equipment: SOFREL S4W 2G modems, limited local monitoring, 3 technicians.

Issues:

40% of stations lack automatic alarms (outages are detected through calls from residents)
The 2G network is being phased out in the region
NIS2 requirement (municipal district serving > 15,000 residents)
Performance contract requiring a service availability rate of > 99.5%

Eziwan Deployment:

80 Eziwan gateways (1 per station) delivered pre-configured within 3 weeks
Migration from S4W systems in 6 weeks (13 stations per week, 2 technicians)
Configuration: 8 to 24 Modbus registers per station, SMS/email alerts
Centralized dashboard: real-time view of all 80 stations, GIS mapping

6-Month Results:

Unplanned service calls reduced by 68% (from 240 to 77 calls per year)
Detection of a major leak in a discharge line (abnormal nighttime flow automatically detected at 2 a.m., repair completed at 6 a.m.)
Documented NIS2 compliance (external audit passed)
Estimated savings: €95,000 per year (avoided service calls + avoided damage)

Compatible Protocols and Equipment

Water Meters

Protocol	Compatible Meters	Collected Parameters
M-Bus (EN 13757)	Sensus iPERL, Itron Actaris BDE, Landis+Gyr E120, Sagemcom	Reading (m³), instantaneous flow rate, alarms (tampering, dry run)
Pulse (digital input)	Any meter with a pulse output (reed switch output)	Cumulative reading, calculated flow rate (number of pulses × volume per pulse)
Modbus RTU	Endress+Hauser Promag, Krohne Optiflux, Siemens Sitrans FM	Flow rate (m³/h), velocity (m/s), temperature, cumulative reading
MBUS LoRaWAN	LoRaWAN meters for areas without coverage	Via LoRaWAN concentrator + Eziwan gateway (MQTT)

Water Sensors

Parameter	Compatible Sensors	Interface
Residual Chlorine	Hach CL17sc, YSI MultiLab, Bürkert Type 8905	Modbus RS-485 or 4-20 mA
pH/ORP	WTW IQ SensorNet, Endress+Hauser CPS11D	Modbus RS-485 or 4–20 mA
Turbidity	Hach TU5200, Yokogawa FLXA21	Modbus RS-485
Conductivity	Endress+Hauser Liquiline CM44	Modbus RS-485
Level	Vega Vegapuls, Endress+Hauser FMR51, Keller Series 26	4–20 mA or Modbus

Water Field Controllers

PLC	Interface	Compatibility
Schneider Electric M340	Modbus RTU RS-485	✅ Tested and validated
Schneider Electric M221/M241	Modbus RTU RS-485 + Modbus TCP	✅ Tested and validated
Siemens S7-1200/S7-1500	Modbus TCP (via Ethernet)	✅ Tested and validated
Lacroix Tbox LT2 / MS3	Modbus RTU / TCP	✅ Compatible
Wago 750-860	Modbus TCP	✅ Compatible
CODESYS Modbus Slave	Modbus RTU / TCP	✅ Compatible

Calculating ROI for a Local Government

Costs Avoided Through IoT Monitoring

Technician Service Calls:

Average cost of an unscheduled service call: €180 to €350 (1.5 hours round trip + diagnosis)
Typical reduction with Eziwan: 60 to 75% of unscheduled service calls avoided
Example: 80 stations, 3 technicians: 240 service calls/year → 77 service calls/year = 163 service calls avoided × €250 = €40,750/year

Damage Avoided (Leaks, Failures, Overflows):

Undetected discharge line leak: 5,000 to 50,000 m³ lost before manual detection
Cost per m³ of treated water: €0.80 to €1.20
Example: 1 leak of 15,000 m³ prevented = €12,000 to €18,000 per year

On-Call Duty:

Reduction in nighttime emergency calls: -40 to 60%
Savings on on-call premiums and overtime: €10,000 to €25,000 per year, depending on the fleet

Regulatory Compliance:

Avoid receiving a formal notice from the ARS due to an undetected threshold violation
Estimated cost of a documented non-compliance: €15,000 to €50,000 (urgent repairs + external audit)

Example of an ROI calculation for 80 stations

Item	Annual Value
Avoided travel	40,750 €
Early detection of leaks	15,000 €
Reduction in on-call fees	15,000 €
Avoided regulatory non-compliance	10,000 €
Total estimated annual savings	80,750 €

Investment	Amount
80 Eziwan gateways + installation	48,000 €
Cloud subscription (80 sites/year)	14,400 €
4G M2M SIM cards (80 sites × 10€/month)	9,600 €
Total investment for Year 1	72,000 €

ROI in Year 1: 80,750 − 72,000 = +8,750 € in the first year ROI starting in Year 2: 80,750 − (14,400 + 9,600) = +56,750 €/year

Funding and Available Assistance

ERDF and Regional Allocations

Projects to modernize remote management systems for drinking water networks may be eligible for ERDF (European Regional Development Fund) funding under the 2021–2027 regional operational programs, specifically under the "Digital Transition of Public Services" priority axis.

Water Agencies

The six French water agencies (Artois-Picardie, Rhine-Meuse, Seine-Normandy, Loire-Brittany, Adour-Garonne, Rhône-Mediterranean-Corsica) offer grants to modernize water network management. Eligibility criteria include reducing leaks (network efficiency), regulatory compliance, and digital transformation.

Contact your local water agency to find out about current programs and the subsidy rates applicable to your project.

Local Investment Support Grant (DSIL) and DETR

The DSIL and the DETR (Fund for Rural Infrastructure) can provide funding for digital projects in rural communities. Projects to modernize water networks using IoT technology align with the “local services” and “digital transition” objectives of these funding programs.

FAQ

Is IoT monitoring eligible for the France Relance Plan or regional grants? Yes, several programs may apply. The DSIL (Local Investment Support Grant) funds local governments’ digital projects. The DETR (Rural Areas Infrastructure Grant) covers rural municipalities. Water agencies (Seine-Normandy, Loire-Brittany, etc.) have specific programs for reducing water loss and self-monitoring. A technical proposal with a quantified ROI (savings from reduced leaks, avoided costs) is generally required.

Is migrating from an existing SOFREL system disruptive? No. The Eziwan gateway connects in parallel with existing SOFREL equipment via Modbus RTU/TCP or 4–20 mA. There is no need to shut down the existing system during the transition. The migration can be carried out in phases: first, data reading; then, a gradual switchover of pilot stations; and finally, complete replacement according to your equipment replacement schedule.

How does the solution meet the ARS self-monitoring reporting requirements? The Eziwan platform allows self-monitoring data to be exported in the required formats (CSV, Excel) with certified timestamps. Performance indicators (loss rates, nominal vs. actual flow, pressure incidents) are automatically calculated from the meter readings and can be extracted for the time periods requested by the ARS.

Conclusion and Next Steps

Modernizing remote management systems for drinking water is no longer an option for French municipalities. The phase-out of 2G networks, NIS2 requirements, ARS self-monitoring requirements, and pressure to reduce operating costs are all converging to make this investment essential.

The good news: ROI is quick (usually less than 18 months), migration from existing systems (SOFREL, etc.) is well-documented and non-invasive, and modern solutions (4G gateway + cloud) are significantly less expensive than first-generation proprietary equipment.

Your next steps:

Audit of your current infrastructure: equipment inventory, identification of 2G modems, mapping of field controllers
ROI simulation: our team can prepare a customized calculation based on your infrastructure
Pilot project: Start with 5 to 10 pilot stations to validate the solution before a full-scale deployment

Contact the Eziwan team for a free audit of your remote water management infrastructure.

Additional Resources

Water & Wastewater Solutions — IoT monitoring of drinking water networks for municipalities
Water Tower Monitoring — remote management of municipal water towers and reservoirs
Wireless M-Bus Meter Reading — automatic water meter reading via radio
Water Tank Monitoring — real-time monitoring of levels and pressures
Pumping Station Solution — remote monitoring and control of pumping stations

Drinking Water Network Monitoring: An IoT Guide for French Municipalities 2026