Method for performance testing of water meters (domestic type)
1996 Edition

To verify water meter performance in line with IS 6784, the test setup must achieve flow rates specified by IS 779:1994, including maximum (Qmax), transitional (Qt), minimum (Qmin), and nominal (Qn) flow rates. Flow is regulated using inlet and outlet valves to stabilize each rate. Meter readings are recorded at the beginning and end of each flow interval, while water volume is concurrently collected in a calibrated tank. The percentage error is then calculated as ((Volume collected - Meter volume) / Volume collected) × 100, with tests performed independently for each flow rate to ensure accuracy across the meter's full operational range.

Metering accuracy evaluation per IS 6784 involves testing flow rates corresponding to Qmax, Qt, and Qmin from IS 779:1994, with optional testing at Qn. Flow adjustments are made using valves to reach these rates. For each flow, meter readings are noted at start and completion, while actual water volume is gathered in a measuring tank simultaneously. The percent error is computed as ((Volume collected - Meter indicated volume) / Meter indicated volume) × 100. Accuracy results are documented separately per flow rate, with the Qmin measurement also confirming the minimum starting flow compliance.

The pressure tightness test aims to confirm that the water meter exhibits no leakage when subjected to 2.0 MPa pressure for one minute. Equipment such as hand pumps, reciprocating pumps, pressure intensifiers, or dead weight pressure gauge testers are used to apply and maintain this pressure steadily. The procedure includes filling the meter with water, applying the specified pressure, holding it for the duration, and inspecting for leaks or pressure drops. A successful test shows no leakage and stable pressure throughout the test period.

According to IS 6784, the temperature suitability test requires immersing a water meter, previously qualified as per IS 779:1994, in a controlled water bath maintained at 45°C ±1°C for a duration of 10 hours. Prior to immersion, any dust caps or devices preventing water entry into the wet chamber must be removed. After the test, the meter is taken out, allowed to return to ambient temperature, and then subjected to flow and pressure tightness tests to verify performance retention. This procedure ensures the meter’s reliability under elevated temperature conditions.

Life testing involves selecting two unopened meters per size and class every six months for endurance evaluation. Depending on the nominal flow rate, meters undergo either discontinuous or continuous testing at specified flow rates and durations defined in the standard's Table 1. Tests include numerous operational cycles with defined interruptions and pauses to simulate extended usage. After testing, meters are reassessed for flow accuracy and pressure tightness, and inspected for mechanical wear. This accelerated testing verifies long-term durability and consistent performance.