An increase in minimum night flow (MNF) is a useful trigger for investigating a district metered area (DMA), but it does not prove a particular physical leakage volume. Industrial night demand, changing reservoir storage, open boundary valves, measurement offset or pressure variation can generate similar trends. A dependable workflow validates the DMA boundary and telemetry before labelling unexplained flow as real loss.
1. Define a measurable hydraulic boundary
A DMA is an area with controlled and documented inflows and outflows. Measure all supply inlets and identifiable transfer outlets; record bypasses, reservoir movements and boundary valve states. One inlet meter cannot represent the zone if unregistered cross-connections exist.
For a defined interval, net inflow can be interpreted as the sum of inlets minus outlets and the rate of increase in stored volume, with an explicit sign convention. Check reverse-flow measurement capability and synchronise time bases before reconciling instruments.
2. Estimate legitimate demand during the night
MNF may mean the lowest recorded interval or a deliberately selected low-demand average, but the method must be consistent. A 02:00–04:00 window may work for many residential areas; a hospital, shift-working plant or irrigation region may have a different low-demand period. Select the window from observed demand patterns.
Legitimate consumption includes residential night use, processes, flushing, tanks and other authorised use. The 2024 Water study on DMA minimum night flow highlights the importance of estimating residential minimum demand statistically; inlet night flow is not automatically all leakage.
3. Worked balance: unexplained night flow
Assume a measured supply-inlet night flow of 12.4 m³/h and independently verified or defensibly estimated legitimate demand of 3.1 m³/h, plus a known 0.8 m³/h transfer. The unexplained remainder is 12.4 − 3.1 − 0.8 = 8.5 m³/h. Treat it as an investigation candidate, not a verified leak.
Multiplying this value by 24 yields an illustrative 204 m³/day only if the same rate persisted continuously. A nighttime observation does not demonstrate such persistence; pressure, demand and storage conditions differ by day, and annual leakage cannot be inferred from one MNF point.
4. Examine pressure, instruments and timestamp quality
Night pressure rises can increase leak rates, yet the pressure–leakage relation depends on pipe condition and failure mechanism. Do not apply a universal coefficient without calibration. Compare pressure and flow on the same timestamp and validity rules.
Check electromagnetic flow meter pipe fill, bonding, zero offset, flow direction and its specified measuring range. If an external RTU or MQTT transport buffers messages, retain actual measured time distinct from receipt time and flag stale or missing data.
5. Design anomaly flags rather than a single threshold
Suppose comparable nights at similar pressure previously showed 5.0 m³/h of unexplained flow and now show 7.5 m³/h: the increase is 2.5 m³/h. A conditional 24-hour equivalent is 60 m³/day; it is not evidence of a new 60 m³/day leak unless continuity and other causes are verified.
Require multiple valid nights, sufficient data completeness, matched pressure bands and relevant adjacent-zone signals where possible. Separate alerts for elevated MNF, telemetry failure, uncertain boundary condition and suspected leakage so teams investigate the right failure class.
6. Combine ATLAS metering with field verification
Compatible ATLAS electromagnetic flow meters can expose measured values through specified interfaces to an RTU or data collection system. Cellular or LoRaWAN connectivity may require external equipment and a project-specific design; it should not be described as an intrinsic feature of every meter.
In acceptance tests verify boundary valves, flow directions, counter reconciliation, pressure points and representative night intervals. A supervised step test or acoustic survey may then localise problems according to utility safety procedures. Analytics prioritises field work rather than replacing leak confirmation.
Frequently asked questions
Is minimum night flow the same as leakage?
No. Subtract legitimate night demand and account for boundaries, storage, pressure and measurement errors.
Can a single anomalous night confirm a burst?
No. Compare trends under similar conditions and verify in the field.
Share your DMA boundary diagram, inlet/outlet flow meter list, pressure points and sample 15-minute data with ATLAS for a system review.
Related ATLAS product 1 · Related ATLAS product 2
All MNF thresholds and volume figures are worked examples, not verified water loss quantities or instrument guarantees.