Manage water
the way you manage
energy
Flow meters, zone sub-metering, leak detection through night flow analysis. A concrete method for hospitality, textile and tertiary buildings, now that water has become a scarce resource.
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In brief
- The problem: water is measured at a single point, once a month. A leak or a drift only shows up on the bill, too late and with no location.
- The solution: measure continuously and per zone with flow meters, compare to expected behaviour, and alert on any anomaly.
- The most reliable signal: the night baseline flow. A flow that persists at night, when nobody is consuming, almost always reveals a leak.
- The real stake: less the savings on the bill than business continuity and compliance, in a context of growing water scarcity.
Why water is becoming critical
Water is no longer a cost. It is a risk to manage.
For decades, water was treated as a cheap commodity, measured once a month and paid without question. That time is over. Resource scarcity, falling water tables and usage restrictions are turning water into a business-continuity factor. A site that runs out of water does not cut its costs: it stops.
Water should be thought of as a risk, not a cost: in most cases a cubic metre of water remains cheaper than a kilowatt-hour, so a purely financial argument is weaker than for energy.
1.1 From cost to risk
The real exposure is not read on the bill, but along three axes: the availability of the resource, regulatory pressure, and reputation. This is the grid a technical manager should have in mind before talking about savings. Each of these axes can, on its own, justify a monitoring project.
- Scarcity and falling groundwater tables
- Restrictions and usage-limitation orders
- Shut-offs that interrupt activity (laundry, dyeing, kitchen)
- Growing water stress across the Mediterranean region
- Abstraction quotas and reporting obligations
- Tightening rules on non-priority uses
- Environmental reporting requirements (ESG, CSRD)
- A growing duty to measure and to justify
- Environmental labels required by clients and groups
- Expectations from textile supply-chain buyers
- Image of a wasteful site in a water-scarce area
- An increasingly scrutinised criterion in tenders
1.2 A normative framework that already exists
Water efficiency has its own international standard: ISO 46001, dedicated to water-use management systems. It follows the same logic as ISO 50001 for energy: measure, define indicators, set targets, improve continuously. Water monitoring is the measurement brick without which this approach stays theoretical.
What you don't see today
One meter, once a month: the blind spot
On the vast majority of sites, water is measured at a single point, the utility meter, and read once a month. A leak or a drift therefore only appears on the bill, often weeks after it started, and with no indication of the zone concerned. You observe. You don't manage.
The monthly reading of a single meter tells you neither where, nor when, nor why water is consumed: it lumps useful uses, leaks and drifts into one late total with no location.
2.1 The monthly reading: what it hides
A slow leak on a buried network can run for months before being spotted, because it drowns in the global total. The table below sums up the difference in diagnostic capability between the two approaches.
| Question | Monthly main meter | Continuous per-zone monitoring |
|---|---|---|
| How much? | Yes, at month end | Yes, in real time |
| Where? | No | Per zone / workshop |
| When? | No | Hourly curve |
| A night leak? | Invisible | Detected |
| Alert delay | Weeks | Minutes to hours |
The 6 chapters that turn reading into an action plan
How monitoring works technically, three sector chapters (hospitality, textile, tertiary), the deployment method, a FAQ and sources.
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Intelligent water monitoring
Intelligent water monitoring is a system that measures consumption continuously and per zone using flow meters, transmits the data, compares it to expected behaviour, and automatically alerts on any leak or drift.
Understanding this chain means knowing where to place a sensor and how to read what it sends back. It breaks down into four links, from the field to the alert.
3.1 Which flow meter to choose
There is no universal flow meter: the choice depends on the nature of the water, the pipe diameter and the precision required. Three technologies cover the vast majority of needs.
| Technology | Principle | Strengths | Limitations |
|---|---|---|---|
| Mechanical (turbine, velocity) | Rotation of a turbine driven by the flow | Simple, economical, proven | Pressure drop, wear, sensitive to loaded water |
| Electromagnetic | Voltage induced by water in a magnetic field | Precise, no pressure drop, handles loaded water | Requires conductive water, higher cost |
| Ultrasonic (transit time) | Measurement of the shift of ultrasonic waves | Wide range, clamp-on (non-intrusive) installation | Cost, sensitive to bubbles and particles |
3.2 The three indicators that matter
Raw data is useless without the right indicators. Three families of KPI structure water management: consumption per zone, night baseline flow, and the consumption ratio.
- Breakdown of water by workshop or use
- Enables cost allocation and comparison
- Surfaces abnormally high uses
- Minimum consumption outside activity (night, closure)
- A non-zero night flow almost always reveals a leak
- The most effective indicator for detection
- Water related to a unit of activity
- Litres per guest-night, per kg of linen, per occupant
- Tracks a drift over time
3.3 Detecting a leak through night flow
The most robust way to detect a leak does not watch the leak, but the flow when nobody is consuming: on a normal site, the flow drops to nearly zero at night. If it stays high, water is going somewhere.
The core brick: anomaly detection
A fixed threshold is not enough, because normal consumption varies by day and by season. Monitoring compares each measurement to an expected behaviour learned from the site's history. A slow drift, a sudden spike or a persistent night flow triggers an alert, before the bill speaks.
Hospitality: the invisible leak
In a hotel, water spreads across many uses active at different hours, which makes drifts hard to spot by eye. The two priority levers are night leak detection and per-zone sub-metering.
4.1 Where water goes in a hotel
- Showers, WCs, taps
- The use most tied to occupancy rate
- Frequent, silent toilet-cistern leaks
- Washing machines, dishwashers, preparation
- Large concentrated consumers
- Easy to sub-meter and track
- Pool make-up water, garden irrigation
- Seasonal consumption
- Abnormal pool make-up signals a basin leak
4.2 The priority lever: the night
A hotel never fully sleeps, but its water flow should drop sharply at night. A leaking cistern, a dripping hose, a burst pipe in the basement: all of this shows up on the night flow curve, well before the bill. Tracking the baseline flow is, in hospitality, the first reflex to put in place.
📊 How much a continuous leak costs
A leak does not stop at night: it runs 24 hours a day, all year round. The formula below gives its volume and cost.
Example: a continuous leak of 50 L/h represents 50 × 24 × 365 = 438,000 litres, i.e. 438 m³ per year. At an indicative rate of €2/m³ (adjust to your contract), that is €876 per year for a single discreet leak, invisible on a monthly reading.
4.3 The ratio to track: litres per guest-night
Relating consumption to the number of guest-nights neutralises the effect of occupancy. A litres-per-guest-night ratio that drifts at constant occupancy signals a problem, even if the overall bill looks stable. It is also an indicator that resonates with hotel groups and feeds environmental-label programmes.
Textile: water at the heart of the process
In textile, water is not a side use but a raw material of the process: washing, dyeing, rinsing and cooling. The stake goes beyond leaks. It is the control of consumption at each production stage and the securing of supply.
5.1 The consuming stages
- Dye baths, pre-treatments
- The biggest consumers of water and energy
- Strong variation by recipe and batch
- Repeated steps, often over-consuming
- A major optimisation opportunity
- Natural candidate for water reuse
- Cooling circuits, boiler house
- Continuous background consumption
- Often overlooked in audits
5.2 The priority lever: sub-metering per workshop
Measuring water at the entrance of a textile site tells you nothing useful. The value comes from sub-metering per machine or per workshop. It allows consumption to be allocated to each stage, equivalent lines to be compared, and a drifting machine to be spotted. It is also the prerequisite for any effluent-reuse project: you only recycle what you can measure.
📊 The reference ratio: litres per kilogram of fabric
The key ratio in textile is specific consumption, expressed in litres of water per kilogram of textile processed.
According to sector references, textile finishing (dyeing and finishing) typically consumes on the order of several tens to more than a hundred litres of water per kilogram of textile, depending on the process, the fibre and the depth of shade. Tracked per workshop and over time, this ratio reveals drifts and compares performance across lines.
5.3 Towards effluent reuse
Part of the rinsing water can be recovered, treated and reinjected into the process. This kind of project rests entirely on measurement: without fine sub-metering of inputs and outputs, it is impossible to size a reuse loop or to prove its gain. Monitoring is the foundation, not the option.
Tertiary: the diffuse consumption
In offices, retail and public buildings, water consumption is lower and more diffuse than in industry, spread across many points with no single dominant use. The logic stays the same: detect the leak and track the drift before they appear on the bill.
6.1 Where water goes in a tertiary building
- The main use, tied to occupancy
- Very frequent toilet-cistern leaks
- Night flow theoretically zero
- Make-up water for cooling circuits
- Continuous and often ignored consumption
- An abnormal make-up signals a blowdown or leak
- Green spaces, catering, cleaning
- Seasonal or intermittent uses
- Automatic irrigation to keep an eye on
6.2 The priority lever: leaks and regulatory tracking
In tertiary buildings, leaks remain the first opportunity, especially on restrooms and cooling circuits. Continuous tracking also documents consumption, which becomes useful as environmental reporting obligations tighten.
Consistency with your energy approach
Water monitoring fits naturally into a performance approach already under way on energy, within a standard such as ISO 50001 or the tracking imposed by building-decarbonisation regulations. The same continuous-measurement logic applies to one more utility, on the same platform.
Deploying a monitoring project
A water monitoring project does not mean instrumenting a whole site at once: it starts small, on the at-risk zones, then expands. Here is the method in five steps.
7.1 How to read a consumption curve
Three signals to spot on a curve. A non-zero night baseline flow indicates a probable leak. A sudden, isolated spike corresponds to a one-off event or a fill-up. A slow, continuous drift over several days signals fouling, a setting that has slipped, or a small leak that is worsening. Each calls for a different action.
7.2 What return to expect
The gain of a water monitoring project is measured on three fronts: leaks avoided, drift corrected, and protection against regulatory risk. The financial return on investment depends heavily on the local price of water and the volume of existing leaks, so it is assessed case by case. But the main value, in a context of pressure on the resource, remains business continuity: ensuring that the water needed for the process will be available and under control.
FAQ, glossary & sources
Frequently asked questions
Glossary
- Flow meter: a sensor measuring the flow of water passing through a pipe.
- Sub-metering: measuring consumption at several internal points, downstream of the main meter.
- Night baseline flow: the minimum consumption measured outside activity, a key leak indicator.
- Specific consumption: water related to a unit of activity (litres per kg, per guest-night, per occupant).
- Alert threshold: the value beyond which a notification is triggered.
- Anomaly detection: comparing the measurement to an expected behaviour to spot a drift.
- Effluent: waste water from a process, potentially recoverable after treatment.
- Clamp-on ultrasonic: a flow meter fitted onto the outside of a pipe, with no intrusion.
- Electromagnetic: a flow meter using the voltage induced by water in a magnetic field.
- m³: cubic metre, unit of water volume (1,000 litres).
- ISO 46001: international standard for water-use management systems.
- ISO 50001: international standard for energy management systems.
Sources and references
- ISO 46001:2019, Water efficiency management systems – Requirements with guidance for use. Reference normative framework for managing water use.
- ISO 50001, Energy management systems. Sister standard, with a measurement and continuous-improvement logic applicable to water.
- Night-flow analysis principle, a recognised method for detecting losses on water networks.
- The specific-consumption ranges for the textile sector are given for guidance only: validate them against your own readings and process data before publication.
Move to smarter water management
Flow meters, sub-metering, leak detection: this guide gives you the method. Our teams can support you in deploying it on your installations.
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