Impact of Large Meter Sizing on Unaccounted For Water. Presented by:

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1 AIDIS AIDIS-USA AIDIS-Interamericana FSAWWA 2004 Seminar Water Losses in Drinking Water Systems Unaccounted for Drinking Water Management and Technological Solutions June 10-12, 2004 Impact of Large Meter Sizing on Unaccounted For Water Presented by: James B. Smith JBS Associates, Inc. Houston, Texas

2 AIDIS AIDIS-USA AIDIS-Interamericana FSAWWA 2004 Seminar Water Losses in Drinking Water Systems Unaccounted for Drinking Water Management and Technological Solutions June 10-12, 2004 Impact of Large Meter Sizing on Unaccounted For Water INTRODUCTION The growing cost of unaccounted for water (UFW) and the impact of water conservation issues have motivated utilities worldwide to implement programs to focus on these problems. In a non-metered society, the primary focus of dealing with UFW is to improve the integrity of the system by locating leaks in the transmission and distribution networks. Many methodologies have been attempted over the years to control leakage in the system, including periodic acoustic soundings, zone or district monitoring, and pressure reduction. In parts of the world that are metered, accurate metering, becomes the barometer for utilities to gauge their operational and financial performance. It is also important to point out that not all leak detection efforts are successful and not all meter replacement programs support water conservation programs or generate revenue. Many factors influence these choices. Metering solutions are not universal. This is illustrated by the different types of meters that exist on the production and distribution side. This problem is further complicated by the wide variance in accuracy, cost and quality of meter types. On the production side, some of the more common types include differential pressure, MAG, ultrasonics, and mechanical or velocity meters such as propellers and turbines. Testing of these meters is being done with pitot rods, portable ultrasonic, portable MAG, portable propeller types, and time-volume checks (generally off of a wet well or ground storage facility). None of these meters is universal and each has its area of application. Under the right conditions, each meter is accurate and under the wrong conditions, each meter is inaccurate. Proper installation and sizing of the source meter as well as the test meter is paramount. The same problem exists on the distribution side. Small meters are represented by positive displacement, multi-jets and single jet meters; where large meters are represented by turbines, compounds, combination, positive 1

3 displacement, multi-jet and single jet meters. The meter application, meter life expectancy, and overall accuracy of these types vary considerably, and the selection of a particular type of meter will depend on a number of factors including water quality, rates of flow, meter quality, meter size and installation. If a meter is undersized, rates of usage may exceed the capacity of the meter and usage may not be recorded. If this process continues the useful life of the meter will be exceeded much faster than expected. The end result is increased UFW and lost revenue. If a meter is oversized, low usage may not be recorded, and UFW and lost revenue increases. Revenue is calculated at the tariff structure. In the Untied States it is not uncommon to see lost water associated with meter error (water and sewer tariff) approaching 20 or 30 times the direct value of lost water associated with leakage (base production costs of energy, chemicals and purchase cost if any). In areas of extreme water conservation this ratio is sharply reduced as production costs increase. Accurate metering is critical. Large Meter Sizing In the past 10 years we have had the opportunity to review consumption patterns on more than 2 million water meters on four continents of various meter sizes and types, and the importance of large meter sizing and installation stands out. The following tables and graphs summarize some of that data. The first table is a composite of 4 cities in the United States that are 100 metered and average about 100,000 population each, with a metered ratio of about 84, reflecting on a water loss of about 16. The table shows that 38 of the total usage is by contributed by only 3.8 of the accounts. A quick glance at the table shows that for each size (above 3/4 inch -20mm) the average usage appears to be lower than one would expect for the size of meter represented. For instance the 1-inch (25mm) accounts have an average consumption of only 13,800 gallons per month (52 m 3 per month). Based on average usages, this could easily be handled by a 5/8x3/4 inch (15mm) meter as long as peak hour flows are met. Categorical Usage Meter Size Inches-(MM) No Gal Mo. M 3 Mo. Usage 5/8 15mm 89, /4 (20mm) 14, (25mm) 9, (40mm) 1, (50mm) 2, (75mm) (100mm) (150mm) (200mm) (250mm) 5 1, Totals 118,843 NA

4 The following table summarizes the findings. A composite of all sizes shows that approximately 80 of all 1-inch (25mm) and larger are considered oversized or may be inaccurate. Oversized meters contribute not only to the unaccounted for water problem, but more importantly may contribute to lost revenue as well. The water tariff structure will determine this. Meter Sizing Summary - I inch (25mm) and Larger Meter Size No. Accounts OK Undersized Oversized Unknown Oversized 1 9,976 1, , , , , , Totals 14,503 2, , Selected meters were logged with rate of flow recorders and each test confirmed that a sizing or accuracy problem existed. The picture at the left shows a typical data-logger and the graph below shows the usage rates over a 24 hour period of time. In this case the 3-inch turbine meter never exceeded 22 gallons per minute (approx. 5.2 m 3 per hour). The meter is rated at 350 gallons per minute or about 80 m 3 per hour. Over 89 of the usage occurs at a flow rate under 5 gallons per minute which is the low end range of that size meter. 26 3" T u rbin e M eter D a ta L o g : P o lic e D e p t CFM :31 PM 1:10 PM 1:49 PM 2:28 PM 3:07 PM 3:46 PM 4:25 PM 5:04 PM 5:43 PM 6:22 PM 7:01 PM 7:40 PM 8:19 PM 8:58 PM 9:37 PM 10:16 PM 10:55 PM 11:34 PM 12:13 AM 12:52 AM 1:31 AM 2:10 AM 2:49 AM 3:28 AM 4:07 AM 4:46 AM 5:25 AM 6:04 AM 6:43 AM 7:22 AM 8:01 AM 8:40 AM 9:19 AM 3" GPM M in. Ga lls (3") 3

5 Caracas, Venezuela In 1999 and 2000 a meter management audit was completed in Caracas, Venezuela by Montgomery-Watson-Harza/JBS. Initially the scope of work was centered on analysis of multi-unit accounts. It soon became apparent, however, that a general review of all accounts was needed in order to determine more fully the impact of multi-unit accounts in and upon the system. Approximately 205,000 records were extracted and reviewed, with approximately 190,000 designated as active. The following table summarizes usage. Usage by Classification CODE CLASS NAME NO. ACCTS AVG M 3 / Mo. ACCTS USAGE 1 Res. 63, Com. 14, Ind-A 29 4, Ind-B 1, Res- Social 32, Oficial 1, Res - Inavi 63, Land M Res-multi 10, M Com-multi M Social-multi 1, TOTALS TOTALS 189, Residential multi-unit accounts were selected for further study in pilot areas for the following reasons: 1. The distribution of sales by classification shows that over 44 of total sales derives from multi-unit accounts. 2. System wide only 19.5 of all customer accounts are metered and read monthly. 43 of Residential Multi-unit accounts are metered, the highest percentage for any category. 3. Approximately 85 of the Bs66 billion in arrears is owed by estimated accounts. However, with the exception of Oficial accounts, the highest arrears per connection were on Residential Multi-unit accounts. 4. Multi-unit accounts were reviewed to calculate average consumption per unit served. The system wide average for all metered multi-unit accounts exceeds 27 cubic meters per month. Un-metered, estimated multi-unit accounts average about 24 cubic meters per month per unit. All multi-unit accounts averaging less than 20 cubic meters per month were extracted for further analysis. The average consumption per unit for metered accounts was compared against the target account averages per unit for each cycle. The difference in consumption then was multiplied by the applicable tariff to estimate potential revenue gain. 5. A final factor was applied to assume a 50 error in either data or methodology. Would it still be cost effective to replace these meters with this factor applied? 4

6 6. There were a total of 989 accounts identified as potential target accounts with a projected revenue increase of about $3 million. The pilot project has not been completed. The analysis showed that that about 5 of the customers consume about 60 of the water. Large meter accounts and consumers are critical. PERCENT DISTRIBUTION OF SALES - METERED ACCOUNTS CUBIC METERS PER MONTH NO. ACCT CUM ACCT CUM USAGE > NUMBER OF ACCOUNTS Metered Ratio s can be Masked by Large Meters In some water systems it is not uncommon to see 1 or 2 of the customers consuming over 50 of the usage. Large meter usage can mask the metered ratio and provide false security to a utility. One City where this is true has about 14,000 metered customers. One customer consumes over 60 of the water. The metered ratio of this city exceeded 91 which is considered excellent. However, when the usage of this one account is taken out of the production/sales equation, the metered ratio drops to 70 reflecting a 30 loss. Percentages can be very misleading, and volume of loss is more important, since a monetary value can be established. The following graph shows the distribution of usage for another City where about 1 of the customers consume 60 of the water. In this particular example, the cost analysis showed that meter error had a 39 times greater value than the direct cost of leakage. Large meter accounts need to be monitored closely. 5

7 Distribution of Usage - All Accounts >1500 Hundred Cubic Feet Cum Cum Usage Water Rate Tariffs and Meter Downsizing Many utilities have minimum bill charges fixed to meter sizes. When meters are downsized, it is possible that the utility will lose revenue with a reduced minimum bill charge. This can be offset by basing the minimum charge on the service line size and not the meter size. The following table is an example of one such case. The table shows that the City would lose approximately $357,000 per year if meters were downsized. They would have to recapture over 100,000 hundred cubic feet per year in sales to offset the reduced minimum bill revenue. Again, a change in the wording of the tariff agreement to base the minimum charge on service line size would reverse this. On the positive side, the utility would save over $250,000 in capital costs when replacing the downsized meters. 6

8 Cost of Downsizing Meters Meter Size Sugg Size No Downsizing Annual Min Bill Hundred Cubic Ft. CCF/Mo/Acct Increase Diff $ Yr Required 1 5/8 or 3/4 1,705 -$ 102,505 29, $ 7,567 2, /8 or 3/ $ 53,301 15, $ 27,337 7, /8 or 3/ $101,543 29, $ 9,677 2, /8 or 3/4 14 -$ 14,742 4, $ 2, $ 20,341 5, $ 3, /8 or 3/4 8 - $ 14,093 4, Totals 2,528 -$357, ,098 NA Meter Sizing and Fire-line Protection Utilities should not size domestic usage based on fire requirements. Massive over sizing of meters will occur with resulting revenue loss. Separate fire-lines may be required. Detector checks may be installed in place of a fire line meter to reduce costs. Water rate tariffs need to be adjusted to deal with separate fire line requirements. 7

9 Meter Selection Proper Meter Selection will depend on several factors: The cost of water The cost of the meter The maintenance costs Utilities ability to maintain multiple types of meters Benefits of Proper Meter Sizing Proper meter sizing reduces capital investment Proper sized meters correctly record water use Proper meter sizing results in more revenue, if tariff structure is set properly. 8