UARL WITH SYSTEM CORRECTION FACTOR

Customise the UARL Equation for your systems using UARL with SCF software

In 1995-99, the 1st IWA Water Loss Task Force developed a basic equation to assess Unavoidable Annual Real Losses (UARL) for whole large water supply systems in good condition with intensive active leakage control.

Calculations were initially limited to systems with more than 5000 service connections, at mid-range operating pressures. Infrastructure Leakage Index (ILI) can then be calculated as Current Annual Real Losses/UARL, for international comparisons of technical leakage management performance.

UARL (m3/day)=

(18 x Lm + 0.8 x Ns + 25 x Lp) x AZP/1000

Lm = Mains length in km
Ns = number of service connections from main to property line
Lp = length of underground private pipes from property line to meter in km
AZP = Average Zone Pressure in metres

More than 20 years later, UARL and ILI are widely used internationally. With improved leakage management some small systems with low pressures, outside original system size and pressure limits, report Current Annual Real Losses (CARL) less than UARL (ILI < 1.0).

The UARL equation’s originator, Allan Lambert, has now introduced 3 additional concepts (FAVAD, Poisson and Pressure:Bursts) to extend limits of application much more widely, using a system-specific System Correction Factor SCF which varies with pressure, system size and pipe materials.

In many situations ( >5000 service connections and/or 45-60m AZP) the original UARL (1999) equation will be confirmed to within ten per cent. Outside these limits, UARL with SCF helps to explain why lower UARL volumes can be achieved in small systems at low pressures, or higher UARL can occur at higher pressures.

UARL with SCF shows customised median UARL burst frequencies on mains and services for each DMA, Zone or whole system

UARL with SCF calculation for each DMA or Zone shows customised UARL volumes and Unavoidable Background Leakage at a wide range of operating pressures, including the current AZP


UARL with SCF calculations for each DMA or Zone quantify results from small reductions in pressure (metres or psi) in either m3/day or USG/day

UARL (USG/day)=

(5.41 x Lm + 0.15 x Nc + 7.5 x Lc) x P

Lm = Mains length in miles
Nc = number of connections from main to curb stop
Lc = length of underground private pipes from curb stop to meter in miles
P = Average Pressure in psi

More than 20 years later, UARL and ILI are widely used internationally. With improved leakage management some small systems with low pressures, outside original system size and pressure limits, report Current Annual Real Losses (CARL) less than UARL (ILI < 1.0).

The UARL equation’s originator, Allan Lambert, has now introduced 3 additional concepts (FAVAD, Poisson and Pressure:Bursts) to extend limits of application much more widely, using a system-specific System Correction Factor SCF which varies with pressure, system size and pipe materials.

In many situations ( >5000 service connections and/or 64-85 psi AZP) the original UARL (1999) equation will be confirmed to within ten per cent. Outside these limits, UARL with SCF helps to explain why lower UARL volumes can be achieved in small systems at low pressures, or higher UARL can occur at higher pressures.

UARL with SCF shows customised median UARL burst frequencies on mains and services for each DMA, Zone or whole system

UARL with SCF calculation for each DMA or Zone shows customised UARL volumes and Unavoidable Background Leakage at a wide range of operating pressures, including the current AZP


UARL with SCF calculations for each DMA or Zone quantify results from small reductions in pressure (metres or psi) in either m3/day or USG/day

  • Each Zone or DMA in a water distribution network has different characteristics, such as density of connections, Average Zone Pressure and mix of rigid and flexible pipe materials on services and mains – UARL with SCF calculates a customised UARL volume target for each zone or DMA in m3 or USG per day.
  • UARL with SCF calculations can be completed for just one DMA or Zone, or for your whole water distribution system.
  • Large Utility clients are increasingly using UARL with SCF calculations to get a complete top down/bottom up customised set of UARL volume targets for every DMA, Pressure Zone and Supply Zone in their water distribution network.
  • SCF reports show Zones or DMAs where a standard 1999 UARL calculation for a Zone or DMA significantly overpredicts UARL volume
  • Use these SCF reports to improve your Active Leakage Control priorities.
  • SCF reports also identify Zones or DMAs where a standard 1999 UARL calculation is unlikely to be achievable at the current Average Zone Pressure, and where parts of the water distribution system might benefit from pressure management.
  • SCF calculations also quantify the benefits of smaller pressure management activities in a Zone or DMA by estimating the reduction in UARL volume that could be achieved by reducing pressure by specific amounts, for example by 1 metre or 5 metres either on a permanent or seasonal basis.
“The SCF is a non-dimensional System Correction Factor that extends the application of the UARL equation for all water utilities by addressing additional interacting factors that more precisely help to determine ‘how low could you go’, also for water utilities with a mature approach to leakage
management. Implementation of the “UARL with SCF” will result in rapid identification of pressure managed zones and/or district metered areas for setting and achieving tailored leakage targets, and for quantification of results from further pressure management.”
“Allan Lambert and Kate Stanton-Davies of Water Loss Research and Analysis Ltd provided great technical support and unbelievable quick answers throughout our long lasting collaboration! As a regulatory agency working closely with more than 800 water distribution systems, the Quebec Water Efficiency team saw a great opportunity to work with them to provide useful data and analysis on water losses for each systems. Thanks to both of them the Quebec Efficiency Strategy have a better understanding of the systems and their way to reach their water loss objectives.”
“UARL with SCF software allows us to further customise UARL calculations for each of 320 individual Zones and Sub-Zones, for the first time. Integrating this methodology within the snapshot ILl concept will result in rapid identification of Zones where we may expect to set and achieve lower leakage targets, and better quantification of leakage and burst reductions from further pressure management. Fine tuning the UARL now is allowing us further scope to further reduce leakage, saving millions of euros in the process.”
“The outcomes of the UARL with SCF research will have a significant positive impact on water loss management in North America, as the FWAS Version 6 has removed all lower limits that previously existed for ‘boundary cases’ in calculating a UARL volume. With over 55,000 water systems in North America, and over 90% of those designated as ‘small systems’ and many others with abnormally high pressures, the WLR&A Ltd research will quite literally have an impact on 10s of thousands of water systems. These systems can now use the FWAS Version 6 to establish a baseline standing, then engage the UARL with SCF web application to refine their understanding for predictive leakage modeling and quantify the scale of improvement opportunity that exists specifically for their system.”
Number of calculationsPrice per calculation £Price per calculation €
1-1008093
101-2007588
202-3007082
>300Contact orders@wlranda.comContact orders@wlranda.com
Pricing Table – UARL with SCF Metric Units
Number of calculationsPrice per calculation USD $
1-100100
101-20095
202-30090
>300Contact orders@wlranda.com
Pricing Table – UARL with SCF US Units
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