Reliable metering systems Neil Macleod
Metering hierarchy • Transfer meters to ensure an accurate determination of SIV • Zone or district meters to facilitate analysis of consumption • Customer meters for billing purposes • Deduction meters for multiple family developments
Transfer meters • High accuracy metering (multiple head ultrasonic or magflow meters) are justified for high volume transfer points • Regular drop testing or electronic calibration is essential • In Durban 17 meters out of more than 80 in total, measure more than 95% of the total SIV. Make use of the Pareto principle !
Zone and district meters • Data logging at this level of measurement is most effective for determination of minimum night flows and ILI values. • These meters should be read on the same day that the customer meters in the zone it supplies are read.
Customer metering 1 • We prepare positive displacement meters to inferential meters for domestic or residential customers • ICI customers are metered using inferential meters primarily • Inferential meters require strict compliance with installation instructions to ensure accuracy
Customer metering 2 • Meter accuracy is affected by water quality, time and the total volume of water that has passed through the meter. • Our domestic meters remain compliant with the Trade Metrology Act until they are about 15 years old. • Positive displacement meters that are 20 years old, under-read by 7% and it is cost effective to change them at that point
Pre-paid or credit meters ? • Prepaid meter installations typically cost in excess of R1500 compared to R500 for conventional installations • Tampering is a consideration if meter installations are not visited regularly • Flow limiters as a credit control mechanism
Flow limiter
Meter reading • Monthly reading and billing based on actual readings and not estimates is essential • Reading rates vary from 200 reads per meter reader per day in CBD blocks to over 700 in townships • Technology choice is critical: minimum features today for a hand held terminal must include; GPS, a camera, sufficient memory to store up to 1000 readings, robust and water proof construction and a 10 hour battery life
Multi-unit metering • Bulk meter in the name of the body corporate • Individual meters to each unit with accounts in the name of the occupants of each unit • A charge of R7 per reading to each customer. • This allows each customer to become a direct customer of the municipality and pay for the actual water used. Credit management is more targeted. • The difference between the total consumption and the sum of the consumption at each unit is billed to the body corporate at ICI rates
performance • Collection rate of about 95% • Bill 98% of urban customers on actual readings each month • Customers still want proof that their meter is read each month • Photographic record makes for unintended efficiencies • Aim to continually improve performance
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