1. Is There Any Relief? A Case Study in Pressure Optimization
95th Annual Conference
Raleigh, NC
November 15 – 18, 2015
Is There Any Relief? A Case Study in Pressure Optimization
Presented by:
Tory Wagoner, P.E./P.L.S
Cavanaugh & Associates, P.A.

3. Four Pillars of Managing Leakage
Active Leakage Control
Existing Real Losses
Pressure
Management
Speed & Quality of Repairs
Economic Level
Unavoidable
Real Losses
This is the toolkit for managing leakage, found in the M36 Manual
It is commonly referred to as pressure management. Personally I don’t love this term, because the pressure is already ‘managed’ in many systems in the US through reservoir level control, pumping and zone PRV settings.
This tool in the toolkit – what we are really talking about here is Advanced PM, or really, Pressure Optimization.
Maintenance
Rehab
Repair
As each component receives more or less attention, the losses will increase or decrease
Source: AWWA Water Loss Control Committee

4. LOW PRESSURE

5. MID PRESSURE

6. HIGH PRESSURE

7. International Tools for Practical Leakage Management
Key to colors
Development and testing
Implementation
Concepts
UK Leakage Control Initiative
IWA 1st Water Loss Task Force
IWA 2nd Water Loss Task Force
IWA Water Loss Specialist Group 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
Component analysis of Real Losses (Bursts and Background Estimates, BABE)
Economic Leakage Levels using minimum total cost approach without pressure management)
Pressure: leak flow rate relationships: Fixed and Variable Area Discharges, FAVAD
Developed by John May
Night flow component analysis using BABE & FAVAD concepts
IWA Best Practice International Water Balance and Terminology
IWA recommended Key Performance Indicators (KPIs) for Non Revenue Water and Real Losses
How low could you go? System-specific equations for Unavoidable Annual Real Losses UARL, and Infrstructure Leakage Index ILI
Economic Intervention Policy for Active Leakage Control based on rate of Rise of Unreported Leakage
Use of Confidence Limits in Water Balance and Night Flow calculations
World Bank Institute Banding System for assessment of Real Loss Technical Management Performance and appropriate actions for improvement
Economic Leakage Levels with and without pressure management
Pressure: burst frequency relationships
Quick predictions for systems with high initial burst frequency
A more generally applicable 2-part equation with a non-pressure-dependent component
Influence of reduced burst frequency on annual repair costs, extension of residual infrastructure life and economics of pressure management
The optimization of pressure has been on the radar for over 20 years in the field of water loss management
In the last 5 to 7 years the understanding of the benefits from PO have risen to a new level, and
Even today that understanding is broadening even further.

8. Let’s briefly look at the 3 basic components of leakage
We see that optimizing pressure is a tool that can affect all three types of leakage

9. FAVAD – Fixed and Variable Area Discharges John May (UK) – 1994
N1 – Exponent as a function of pipe type
LeakagePost/LeakagePre = (PressurePost/PressurePre)N1
Early work focused on establishing the relationship between pressure and leakage rates,
To reliably predict the affects of leakage reduction from pressure reduction
Source: Lambert 2003

11. NEW PIPES, GRAVITY SYSTEM, NO SURGES
When new mains and services are laid,
they are designed to withstand existing system pressures
with a large factor of safety, so failure rate is low
NEW PIPES,
GRAVITY SYSTEM
FAILURE
RATE
PRESSURE

12. NEW PIPES, SYSTEM WITH SURGES
If the new pipe system experiences surges (pressure
transients), the Factor of Safety will be reduced, but the
failure rate should remain quite low.
NEW PIPES,
SYSTEM WITH SURGES
FAILURE
RATE
PRESSURE

13. COMBINATION OF FACTORS CAUSES INCREASED FAILURE RATES
As the pipes deteriorate through age (and possibly corrosion), and other
local and seasonal factors, the pressure at which failure occurs
gradually reduces until at some point in time, burst frequency starts to
increase significantly
LOW TEMPERATURES
GROUND MOVEMENT
TRAFFIC LOADING
AGE + CORROSION
COMBINATION OF FACTORS
CAUSES INCREASED
FAILURE RATE
FAILURE
RATE
PRESSURE

14. PRESSURE MANAGEMENT STEP 1: REDUCE SURGES
The first step in pressure management is to check for the presence
of surges; if they exist, reduce the range and frequency of surges
LOW TEMPERATURES
GROUND MOVEMENT
AGE + CORROSION
STEP 1: REDUCE SURGES
TRAFFIC LOADING
FAILURE
RATE
PRESSURE

15. PRESSURE MANAGEMENT STEP 2: REDUCE EXCESS PRESSURE
Next, identify if the pressures at the critical point are higher than
necessary; if so, reduce the excess by pressure management, to
avoid operating the system close to pressures that will cause failures.
LOW TEMPERATURES
GROUND MOVEMENT
AGE + CORROSION
STEP 2: REDUCE
EXCESS PRESSURE
TRAFFIC LOADING
FAILURE
RATE
PRESSURE

16. ALTERNATIVE GENERAL APPROACH TO TEST DATA ANALYSIS AND PREDICTIONS
If the current failure rate is comparatively high (red circle), then quite a
small % reduction in pressure (to the blue circle) may produce a large
reduction in burst frequency. But if the burst frequency is already quite
low (blue circle), further pressure reductions may not greatly reduce
the current burst frequency, but may extend infrastructure life
FAILURE
RATE
PRESSURE

17. SIMPLE APPROACH TO IDENTIFY ZONES WITH GOOD POTENTIAL FOR REDUCTION OF BURSTS ON MAINS, AND ON SERVICES
DON’T mix mains and services data – each can respond differently
UARL reference burst frequencies for
infrastructure in good condition:
Mains 13 per 100 miles/year
Connections 2 per 1000 conns/year
FAILURE
RATE
PRESSURE
Source: Thornton & Lambert, IWA Water Loss Bucharest, Sep 2007

18. BREAK FREQUENCY PREDICTION
Source: Thornton & Lambert 2006

19. Pressure management has been studied and implemented worldwide but not as much in North America
Case studies have identified 4 major impacts of Pressure Management
* Reduction of breaks (mains & services);
* Reduction of real loss (leakage);
* Reduction of energy costs (less pumping);
* Extension of asset life;
In this chart of breaks, the impacts on breaks can clearly be seen;
Very simple illustration, how many here have most of their breaks happen at night?
What happens at night? Consumption goes down which causes what to go up? Pressure…..
Increased pressure causes more breaks, so the simple approach is to make the connection that reducing the pressure would also reduce the number of breaks.

21. Energy Savings After Pressure Management Avg. Pressure 75 psi
Water Pumped into Zone
After Pressure Management
Avg. Pressure 75 psi
Total Consumption = 500 MG/year
Breaks/year = 10
Annual Real Losses = 40 MG/year
Total Water Pumped = psi
Less Water Pumped = Energy Saved
Water Pumped at lower pressure = Energy Saved
Pressure Zone #1
Avg. Pressure 100 psi
Total Consumption = 500 MG/year
Breaks/year = 15
Annual Real Losses = 50 MG/year
Total Water Pumped = psi
Critical Point – Minimum Delivery Pressure
Real Losses = Leaks

22. Pressure Optimization
Customer Svc
Fewer Outages &
Plumbing Breaks
Risk –
Catastrophic Breaks
Non-Revenue Water
Pressure Optimization
Repair Costs
Energy Costs
Energy Costs
Deferred Asset
Replacement

23. CITY OF ASHEVILLE – CASE STUDY

24. Which zone do we select? Zone Selection Criteria:
Are there any continuously pumped zones?
Potentially lower capital implementation costs
Higher level of potential energy savings
Pressure Logging
Average Zone Pressure & Critical Pressure logs identify if there is pressure that can be reduced
Break Frequencies
Pressure Dependent Main line breaks
Pressure Dependent Service line breaks
Comparison to “Unavoidable” Levels

26. DMAs move the City from “periodic survey” to “continuous monitoring”
DMAs move the City from “periodic survey” to “continuous monitoring”. The implications of this are HUGE.
Strategic intervention
Optimization of leak team resources

31. Zone #1 - Haw Creek Operating Conditions:
Continuously Pumped – (4) 30 HP Pumps
Controlled by discharge pressure
Lower Sondley PRV – Backup supply
Lower Sondley PRV
Booster Pump

32. Pressure Logs:

33. Zone Baseline: Field Testing: Low Reported Break Frequencies
No Active Leak Detection
Excess Pressure at Critical Points
Field Testing:
Goal – How much background leakage?
Initial flow/pressure/consumption
Active Leak Detection #1
Active Leak Detection #2
Additional flow/pressure/consumption

34. Results: Ave. Zone Pressure (Maple Ave.) 192 PSI (avg)
 Initial Field Testing – May 26, 2015
Ave. Zone Pressure (Maple Ave.)
192 PSI (avg)
Ave. Critical Pressure (Lower Sondley Estates)
92 PSI (avg)
Ave. Supply Volume
83 gpm
Ave. Customer Consumption
11 gpm
Potential Leakage
72 gpm
Survey
Leaks Found/Repaired
Leakage Estimate #1 6
24 gpm (estimate of 4 gpm/leak) #2 3
12 gpm (estimate of 4 gpm/leak)
Total 9
36 gpm (estimate of 4 gpm/leak)
Second Field Test – July 31, 2015
Ave. Zone Pressure (Maple Ave.)
196 PSI (avg) / 201 PSI (night)
Ave. Critical Pressure (Lower Sondley Estates)
100 PSI (avg) / 105 PSI (night)
Ave. Supply Volume
47.5 gpm
Ave. Customer Consumption
13.9 gpm
Potential Leakage
33.6 gpm

35. Pre/Post Leak Detection & Repair Flow Logs:

36. Business Case:
With Sunk Cost
Without Sunk Costs

37. Dec 8-9, 2015
gawp.org
Conference & Exposition
Over 60 speakers from the United States and around the world
Technical sessions on innovations in water auditing, loss control program implementation, addressing Non-Revenue Water through billing, theft, metering, leakage, pressure, energy and asset management, and regulatory policy development across North America
Case studies for growing implementation of established IWA/AWWA best practices and innovations for Water Loss Management

38. Questions?
Contact: Tory Wagoner, P.E.