Water Meters (Bulk Type)
1981 Edition

IS 2373 permits the use of specific materials for bulk water meter components to ensure durability and corrosion resistance. For the casing, materials include cast iron (Grade FG 200 as per IS:210-1978), bronze (Grade 2 according to IS:318-1962), brass (Grade 3 per IS:292-1961), and ductile cast bronze (DCB 2, IS:1264-1981). Internal parts like the body can be made from bronze, brass, or DCB 2, with enclosed meters requiring a brass liner at least 1.5 mm thick (IS:410-1977). All materials must be non-toxic, corrosion-resistant, and should avoid dissimilar metal contact to prevent electrolytic corrosion, ensuring reliable and safe operation.

The standard defines minimum starting flow as the lowest flow rate at which the meter begins meaningful registration, varying by nominal size and meter type. For vane-wheel meters, starting flows range from 250 L/hr (50 mm) up to 6,400 L/hr (300 mm), while helical types start at higher thresholds, from 500 L/hr (50 mm) to 14,000 L/hr (300 mm), with larger sizes specified accordingly. Capacity ratings include nominal maximum discharge values without excessive headloss, for example, 30,000 L/hr (vane-wheel, 50 mm) and 50,000 L/hr (helical, 50 mm), scaling upwards to millions of liters per hour for larger sizes. Intermediate capacities are also defined for performance assessment across flow ranges.

IS 2373 requires several testing categories to confirm compliance: type tests, production routine tests, and acceptance tests. Type tests involve sampling two meters for 50 mm sizes and one meter for sizes 80 mm and above, randomly selected from production. Testing includes minimum flow detection, loss of head measurement at specified flow rates, accuracy verification at various ranges, hydrostatic pressure testing for leak and strength evaluation, and temperature suitability assessments. Additionally, ease of maintenance and reassembly is evaluated. Detailed reports documenting dimensions, tolerances, and water quality used accompany these tests, ensuring meters fulfill design, accuracy, and durability criteria.

Frost protection is not universally mandatory under IS 2373 but is required for meters susceptible to frost-induced damage. The purchaser must specify whether frost protection is needed at the time of ordering. Recommended protective devices include high-quality rubber pads that allow for water expansion during freezing, collapsible metal rings that enable pressure relief by lifting the meter's top plate, and metal discs incorporated in the meter body that yield under frost pressure to prevent damage. It's critical that any damaged frost protection components be replaced promptly to avoid meter failure or water loss.

The standard mandates sealing provisions to secure the measuring unit, registration box, and meter cap against unauthorized access. Sealing holes must be present on the meter, allowing the use of corrosion-resistant sealing wire such as tinned copper to ensure durability. Where locking is required, the registration box lid must have a hole at least 4 mm in diameter to accommodate a padlock. The seal system must be designed so that any access attempts are evident through broken seals, ensuring tamper resistance while maintaining operational accessibility when authorized.