WaterSight - Estimating Night Consumption

Product(s): WaterSight
Version(s): 10.00.
Area: Documentation


Quantifying night consumption can be helpful for example to better assess the minimum flow that is due to real losses (or real losses flow) for each zone.

The minimum nightly flow (MNF) occurs when the consumption is the lowest inside the zone, and usually this occurs during the night between 2 AM and 5 AM where most people are sleeping and therefore most flow is assumed to be real losses (burst leakage and background leakage), as represented in figure below.

This assumption however can not be applied to some specific zones where night consumption can be very significant such as: industrial zones or areas with bars and hotels or tourist places.

For zones where consumption is not significant during the night, some reference values for night consumption during the MNF period are somewhere between 10% and 30% of the total minimum flow of the zone. This percentage can be defined by the user in the Zones administration, in case the real losses method based on the MNF is selected. If no value is defined WaterSight will assume zero, and a conservative value (overestimated) for the real losses component will be calculated. For more information about real losses calculation in WaterSight, take a look at this article

Although defining a value between 10% and 30% for the night consumption can be a reasonable first estimation for most zones (except those zones with significant night consumption as referred above), for more accurate results it is important to have better knowledge of night consumptions inside each zone. Below are listed some steps can be done to better assess night consumption.

Using Smart Metering data (AMI)

In the case smart metering is available for all or almost all customers inside the zone and ideally with a registration frequency of 15 minutes or less, those automated readings can be used to assess the total night consumption for the zone. Because each customer will consume at different hours during the night, a typical approach is to calculate the average night consumption for each customer for the period between 2 and 5 AM, and then sum all values.

In case smart metering data is only available for a small percentage of the customers inside the zone, and as long as those customers are representative of the type of customers that exist on that specific zone (for example if a zone is residential, it is important that those readings are from residential customers), a typical approach is to:

  • calculate the average night consumption for each customer for the period between 2 and 5 AM
  • calculate the global average value based on each customer night consumption
  • multiply the global average obtained by the total number of customers inside the zone to obtain the total night consumption
  • calculate the percentage of  the MNF that is due to consumption by dividing the total night consumption by the zone MNF (zone minimum flow for each month is available in Zone Report, under Daily Minimum tab)

Large Customer Measurement campaigns

If smart metering is not available at large customers, it may be important to assess night consumption for these specific customers in order to understand if they can have a big impact on the zone minimum flow or not. One option is to temporarily install portable flow data loggers at those customers to understand their impact on the zone minimum flow. Because data loggers can be portable, having few of them may be enough to cover most of them (although it can take some time). 

Using Reference Values

In case smart metering is not available at all, an approach could be using reference values. To note that night consumption values can differ significantly from region to region and also depend on type of system (urban or rural). Below are listed some reference values from different studies that include different regions:



Night consumption (l/customer/hour)

United Kingdom

UK water industry (2002)

Detached house: 2.1 – 3.4

Townhouse: 2 -2.8

Terraced: 1.9-2.5

Apartment: 0.7-1.9

United Kingdom

Fantozzi & Lambert (2012)

Domestic: 1.7

Non-Domestic: 7.4


USEPA (2010)

Countryside: 5.68


Hunaidi & Brothers (2007)



Fantozzi & Lambert (2012)



Fantozzi & Lambert (2012)


South Africa

Mckenzie (1999)



Fantozzi & Lambert (2012)

Domestic: 1.4


Mutikanga (2012)

3 - 10

To calculate the zone night consumption you would need to extrapolate the capita values listed above to your system, and multiply the reference value by the total number of customers inside the zone. Please note that most of the values listed above are specifically for domestic customers, so if there are large customers inside the zone those may have big influence on the minimum flow. 

For more information about WaterSight, please go to OpenFlows WaterSight TechNotes and FAQ's