Page 209 - Water Loss Control

Contr olling Appar ent Losses—Customer Meter Inaccuracy 183

Percent of Time Range, gpm Average, gpm Percent Volume ∗
15 Low 0.50–1.0 0.75 2.0
70 Medium 1–10 5.00 63.8
15 High 10–15 12.50 34.2

∗ Percent volume refers to the proportion of water consumed at the specified flow rate, as compared to
the total volume consumed at all rates. In this example, only 2.0 % of the total water consumed occurs
at the low-flow range of approximately 0.5–1.0 gpm.
Instead of using the percentage of volumes shown here, you may compute your own percentage
volume data. Using special dual-meter yokes and recording meters, you can determine the actual
flow rates for your water meters.
Source: Ref.1
TABLE 12.3 Weighting Factors for Flow Rates Related to Volume Percentages for 5/8- and 3/4-in
Water Meters

Test Flow Rates Mean Registration, percent
Low flow (0.25 gpm) 88.8
Medium flow (2.0 gpm) 95.0
High flow (15.0 gpm) 94.0

Source: Ref. 1
TABLE 12.4 Mean Meter Testing Data from a Random Sample of 50 Meters for County Water
Company

Total Volume at Meter
Sales Flow Rate Meter Error
Percent Volume † (Vf) Registration Meter Error (ME) (ME)
Volume ∗ (Vt) (%V ë Vt) (R) ‡ ME = Vf/(0.01R) – Vf milion
(%V) milion gal milion gal percent milion gal gal
2.0 2,318.8 46.38 88.8 [(46.38/0.888) – 46.38] 5.85
63.8 2,318.8 1,479.39 95.0 [(1,479.39/0.95) – 1,479.39] 77.86
34.2 2,318.8 793.03 94.0 [(793.03/0.94) – 793.03] 50.62
Total Residential meter error (line 8)……………………………………………………… 134.33

∗ From Table 12.3.
† Based on residential water sales data in Table 12.2.
‡ From Table 12.4.
Source: Ref. 1
TABLE 12.5 Calculation of Residential Water Meter Error