Water Meters (Domestic Type)

IS 779: Scope - Key Specifications & Tables

1. Meter Size & Dimensions (Clause 9.1, Table 2)

• Meter size correlates with nominal flow rate (Qn, kl/h).
• Overall dimensions (Length L, Width W, Height H1, H2 in mm) fixed per size.
• Thread sizes and minimum thread lengths specified.
• Example:

2. Flow Rates (Clause 12.2.1, Table 3)

• Defines Minimum Starting Flow (Qmis), Transitional Flow (Qtr), and Maximum Flow (Qmax) per meter size and class (O, A, B).

3. Verification Scale Interval (Clause 8.3, Table 1)

• Max verification scale interval (litres) varies by meter size & class.

4. Sampling for Acceptance (Clause 12.2.2.3, Table 4)

• Specifies sample

IS 779: References - Key Tables & Specifications

1. Meter Size & Dimensions (Clause 9.1, Table 2)

• Nominal Flow Rate (Qu) linked to meter size.
• Threads and dimensions standardized.
• Dimensions in mm:

• Note: Meters supplied with nuts & nipples unless specified.

2. Sampling & Acceptance Criteria (Clause 12.2.2.3, Table 4)

IS 779: Terminology and Definitions - Key Specifications

• Meter Size & Dimensions (Clause 9.1, Table 2):
  Meter size correlates with nominal flow rate (Qn, kl/h). Dimensions include thread length and overall size (L, W, H).
  Example for 15 mm meter:

  • Threads: GEB
  • Nominal Flow Rate: 1.5 kl/h
  • Thread Length: 10-12 mm
  • Length (L): 250 mm (with nipples), 165 mm (without)
  • Width (W): 110 mm
  • Height (H1, H2): 50 mm, 180 mm

• Flow Rates (Clause 12.2.1, Table 3):
  Defines minimum starting flow rate (Qmis), transitional flow rate (Qi), and maximum flow rate (Qmax) for classes O, A, B.
  Example for 15 mm meter:

  Class	Qmis (l/h)	Qi (l/h)	Qmax (kl/h)
  O	90	180	3
  A	60	150	3
  B	30	120	3

• Sampling & Acceptance (Clause 12.2.2.3, Table 4):
  Specifies sample sizes and acceptance/rejection numbers for lot sizes.
  Example: For lot size 51-150, first sample = 13, acceptance number = 0, rejection number = 2.

Summary Table: Meter Size vs Nominal Flow and Dimensions

Classification of Water Meters as per IS 779

Water meters are classified based on maximum verification scale interval and metrological characteristics into:

• Class O
• Class A
• Class B

Key Specifications & Tables

1. Nominal Sizes (Clause 4.1)

• Sizes: 15, 20, 25, 40, 50 mm
• Nominal size = nominal bore of end connections

2. Flow Rates (Table 3)

3. Meter Dimensions & Nominal Flow Rates (Table 2)

IS 779: Key Materials Specifications and Tables

Materials References (Annex A, Clause 2)

IS 779 refers to various Indian Standards for materials used in water meters:

Meter Size & Dimensions (Clause 9.1, Table 2)

IS 779: Construction Requirements - Key Formulas, Tables, and Specifications

1. Sample Size and Acceptance Criteria (Clause 12.2.2.3, Table 4)

2. Meter Size, Threads, Flow Rates & Dimensions (Clause 9.1, Table 2)

IS 779 - Key Formulas, Tables & Specifications for Design and Dimensions

1. Meter Sizes and Dimensions (Clause 9.1, Table 2)

• Note: Meters supplied with nuts & nipples unless specified.

2. Flow Rate Parameters (Table 3, Clause 12.2.1)

Key Specifications & Formulas for Indicating Devices (IS 779)

1. Rotation & Graduation (Clause 8.2.2)

• Indicators with pointers rotate clockwise.
• Each scale division represents:
  [ \text{Value per division} = 10^n \text{ litres}, \quad n \in \mathbb{Z} ]
• Scales are either:
  • Graduated in litres, or
  • Accompanied by a multiplying factor (e.g., ×0.001, ×0.01, ×0.1, ×1, ×10, ×100, ×1000).

2. Colour Coding (Clause 8.2.1)

• Kilo-litres and multiples: Black pointers/digits.
• Sub-multiples of kilo-litres: Red pointers/digits.
• Minimum digit height on drums: 4 mm.
• Digital indicators: digits move upward in value; lower digit completes last 1/10th travel as next higher digit advances.

3. Frost Protection Devices (Clause 7.15)

• Use rubber pads or collapsible metal rings to accommodate water expansion on freezing.
• Damaged parts must be replaced immediately.

4. Meter Size & Dimensions (Clause 9.1, Table 2)

IS 779: Meter Size and Overall Dimensions (Clause 9.1)

Key Specifications from Table 2 (All dimensions in mm)

• Note: Meters are supplied with nuts and nipples unless otherwise specified.
• Tolerance on Length (Clause 9.1.1):
  • With nipples: ±5 mm
  • Without nipples: +0, -2 mm

Additional Notes:

• Nominal size corresponds to the nominal bore of end connections.
• Meter sizes available: 15, 20, 25, 40, 50 mm.

Visual Reference (Fig. 1 - Overall Dimensions)

graph LR
A[Length L] --> B[Width W]
B --> C[Height H1]
B --> D[Height H2]

• L: Length of meter body
• W: Width of meter body
• H1, H2: Heights as per meter design

For detailed thread lengths and dimensions, refer to Table 2 in IS 779

IS 779: Technical Characteristics Summary

1. Tolerance on Overall Length (Clause 9.1.1)

• With nipples: ±5 mm
• Without nipples: +0 / -2 mm

2. Meter Size, Threads, Nominal Flow Rates & Dimensions (Table 2)

• Note: Meters usually supplied with nuts and nipples unless purchaser specifies otherwise.

3. Flow Rate Characteristics (Table 3)

IS 779: Metering Accuracy - Key Points

1. Metering Accuracy Limits (Clause 11.1)

• Lower flow region (Qmin ≤ Q < Qt): ±5% error allowed.
• Upper flow region (Qt ≤ Q ≤ Qmax): Error limits as per IS 6784:1984.

2. Flow Rate Definitions (Table 3)

3. Testing Requirements (Clause 12.2.1 & 12.4.2)

• Type Tests: 3 meters of same size/class tested for loss of head & accuracy.
• Flow Test: Measures pressure loss, metering accuracy, minimum starting flow, and temperature suitability.
• Preconditioning: Flow at nominal rate for 2 hours before testing.

4. Meter Size & Nominal Flow Rate (Table 2)

IS 779: Testing Requirements Summary

1. Samples for Tests (Clause 12.2)

• Submit 3 water meters of the same size & class.
• Provide 6 copies of detailed manufacturer specs including:
  • Loss of head curves
  • Accuracy curves
• Send to a recognized testing authority for type tests.

2. Type Tests (Clause 12.4 & Table 12.2.1)

3. Test Report (Clause 12.5)

• Test reports must comply with IS 6784:1984.

Key Notes:

• Minimum Starting Flow Rate (Qmis): Lowest flow at which meter starts registering.
• Transitional Flow Rate (Q): Flow between minimum and maximum for accurate measurement.
• Maximum Flow Rate (Qmax): Max flow meter can measure without damage.

flowchart LR
    A[Submit 3 meters + 6 spec copies] --> B[Testing Authority]
    B --> C[Type Tests]
    C --> D[Measure Qmis, Q, Qmax]
    D --> E[Prepare Test Report as per IS 678

IS 779: Selection, Installation and Maintenance of Domestic Water Meters

1. Selection

• Choose meter type based on flow characteristics and connection type.
• Refer Annex D for detailed guidelines on selecting meters to ensure proper duty and minimal maintenance.
• Meter size correlates with nominal flow rate (Qn), see Table 2 below.

2. Installation

• Follow direction of flow marked on meter.
• Flush pipeline thoroughly before installation.
• Install inferential meters horizontally with dial facing upwards.
• Do not remove meter strainer.
• Use nuts and nipples unless specified otherwise.
• Refer installation drawing supplied with the meter.

3. Maintenance

• Regularly check meter seals and serial numbers.
• Verify test certificates for pressure tightness, accuracy, and minimum starting flow.
• Follow checklist in Clause 13.2 for inspection and maintenance.

Key Table: Meter Size, Threads, Nominal Flow Rates & Dimensions (Table 2 excerpt)

Sampling for Acceptance (Table 4 summary)

• Lot size determines sample size and acceptance/rejection criteria.
• Example: For

IS 779: Referenced Indian Standards & Key Specifications

Referenced Indian Standards (Annex A)

Sample Size & Acceptance Criteria (Clause 12.2.2.3, Table 4)

Materials for Body and Components (IS 779)

1. Material Specifications:

• Body Material:

  • Free from defects like blow-holes, spongy structure.
  • No repairs by plugging, welding, or adding materials.
  • Internal shape ensures smooth water flow and easy dismantling. (Clause 7.2)

• Plastic Components:

  • Must not affect water potability.
  • Minimum elongation: 15% on 150 mm specimen (per IS 2267:1972 A-7).
  • Water absorption ≤ 0.6% by weight after 24h immersion (IS 2267:1972 B-7).
  • Withstand temperature up to 55℃ without deformation or softening. (Clause 6.1.1)

2. Referenced Material Standards (Annex A):

3. Summary Table for Plastics (Clause 6.1.1):

This ensures durability, safety, and compliance for water meter components per IS