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1.water Supply Distribution LinesWater distribution systems operate under pressure to deliver potable water directly to consumers.

• Network Configuration:

  • Dead-End (Tree) System: Single main split into branches; low cost, but prone to stagnation at terminal points.

  • Gridiron System: Interconnected loops ensuring multi-directional flow, maintaining uniform pressure and uninterrupted supply during repairs.

• Separation Rules (Health & Safety):

  • Vertical Clearance: Water mains must be placed above sanitary sewers (minimum 0.5 m clearance) to prevent contamination if pressure drops.

  • Horizontal Distance: Kept at least 3.0 m horizontally from sewer lines and 1.0 m from electrical/telecom conduits.

• Pipe Materials & Selection:

  • Ductile Iron (DI): Primary choice for high-pressure municipal trunk mains.

  • High-Density Polyethylene (HDPE) / uPVC: Preferred for distribution sub-mains due to flexibility and corrosion resistance.

    2. Service Ducts under the Road (Culverts & Crossings)

    Service ducts run perpendicular or parallel beneath road pavements, housing utilities so crews can lay or repair cables without cutting the road surface.

    • Types of Road Crossings:

      • Precast Concrete Box Ducts / Pipe Sleeve Banks: Multi-bay RCC conduits placed beneath the road sub-base.

      • Underground utilities requiring clear horizontal and vertical separation. Source: Stephen Barnes / Getty ImagesTrenchless Technology (HDD - Horizontal Directional Drilling): Used for retrofitting utility conduits under existing roads without surface excavation.

    • Structural Protection Requirements:

      • Must withstand vehicular wheel loads (designed for IRC Class AA / Class A loading).

      • Minimum cushion depth of 0.9 m to 1.2 m from the road surface to the top of the duct to prevent impact cracking.

        

        Underground utilities requiring clear horizontal and vertical separation. Source: Stephen Barnes / Getty Images

        Utility	Typical Trench Depth	Horizontal Placement in RoW	Protective Measures
        Water Supply	1.0 m – 1.5 m	Beneath footpaths / service lanes	Pressure testing, air release valves
        HT / LT Electrical	0.9 m – 1.2 m	Near property boundary / road shoulder	Red warning tape, RCC protection tiles
        Telecom / Fiber	0.9 m – 1.0 m	Opposite side of electrical lines or separated	Yellow/Orange HDPE ducts, marker posts
        Service Ducts (Road Crossings)	1.2 m – 1.8 m	Perpendicular at regular intervals (every 100 m–200 m)	Heavy-duty concrete encasement (NP3/NP4)

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