Code of practice for water-proofing of underground water reservoirs and swimming pools

IS 6494: Scope Summary & Key Specifications

IS 6494 covers waterproofing of underground water reservoirs and swimming pools, focusing on ensuring water-tightness to prevent leakage and infiltration.

Key Points from Scope:

• Applies to reinforced concrete structures for liquid storage.
• Emphasizes impervious concrete using:
  • Properly graded aggregates.
  • Suitably designed concrete mix.
  • Thorough compaction (internal vibrator or slow hammering of forms).
• Includes waterproofing treatments like bitumen mastic, felts, and integral waterproofing compounds.

Relevant Specifications & References:

Important Workmanship Clause (5.1):

• Concrete must be well compacted, especially around reinforcement and embedded fixtures.
• Use internal vibrators or slow hammering of forms for inaccessible areas.

Typical Concrete Mix Design Considerations for Impervious Concrete:

flowchart TD
    A[Waterproofing Scope] --> B[Impervious Concrete]
    B --> C[Proper Mix Design]
    B --> D[Compaction Techniques]
    B --> E[Waterproofing Treatments]
    E --> F[

IS 6494: Key Formulas, Tables & Specifications for Structure, Design & Construction

1. Structural Requirements (Clause 2.1)

• Follow IS 3370 (Part 1)-1965 for reinforced/ plain concrete design for liquid-retaining structures.
• Ensure water-tightness by proper concrete mix, compaction, and curing.

2. Materials Specifications

3. Design Considerations

• Use reinforced concrete with adequate cover to reinforcement for durability.
• Follow IS 3370 for liquid-retaining structures design stresses and crack control.
• Steel reinforcement should meet IS 432 or IS 1786 standards.

4. Construction Details

• Proper waterproofing treatment using bitumen mastic (IS 5871).
• Ensure joints and construction sequences minimize leakage.
• Regular inspection and rectification of defects during construction.

Example: Basic Water-Tightness Formula (per IS 3370)

[ \text{Maximum permissible crack width} \leq 0.2 \text{ mm (typical for water tanks)} ]

flowchart TD
    A[Material Selection] --> B[Concrete Mix Design]
    B --> C[Reinforcement Detailing]
    C --> D[Construction & Waterproofing]
    D --> E[Inspection & Maintenance]

Summary: IS 6494 mandates adherence to IS 3370 for design, IS 432/1786 for steel, IS 269/455/1489 for cement, and IS 5871 for waterproofing to ensure durable, water-tight underground reservoirs and pools.

Key Materials Specifications from IS 6494 (Relevant Clauses)

1. Steel Reinforcement

• Must comply with:
  • IS 432 (Part 1)-1982: Mild steel & medium tensile steel bars
  • IS 432 (Part 2)-1982: Hard-drawn steel wire
  • IS 1786-1985: High strength deformed steel bars and wire
• Permissible stress in steel reinforcement as per Clause 2.2.2 follows IS 3370 (Part 2)-1965.

2. Cement

• Ordinary and low-heat Portland cement: IS 269 (third revision)
• Portland slag cement: IS 455 (third revision)
• Portland pozzolana cement: IS 1489 (second revision)

3. Aggregates

• Use well-graded aggregates complying with:
  • IS 383 (second revision) for coarse and fine aggregates
  • IS 2386 (Part 3) for specific gravity, density, voids, absorption, bulking

4. Bitumen and Waterproofing Materials

• Bitumen mastic: IS 5871-1970
• Bitumen felts for waterproofing: IS 1322 (third revision)
• Glass fibre base coal tar pitch and bitumen felts
• Industrial bitumen: IS 73 (revised)

Important Notes on Workmanship (Clause 5.1)

• Use properly graded aggregates.
• Ensure thorough compaction using vibrators or slow hammering for inaccessible areas.
• Concrete must be worked well around reinforcement and embedded fixtures for imperviousness.

Summary Table: Material Standards

IS 6494 Waterproofing Treatment: Key Points

1. Waterproofing Methods (Clause 4.4)

• Membrane type waterproofing is emphasized.
• Chemical injection treatment is included for crack sealing.
• Bitumen felts and glass fibre reinforced bitumen membranes are standard materials.

2. Protective Brick Wall (Clause 5.8)

• A protective brick wall is recommended over waterproofing layers to prevent damage.
• Typical detail shown in Fig. 2 for underground reservoirs/swimming pools on piles.

3. Materials Specifications

• Bitumen felts as per BIS specifications (third revision).
• Integral cement waterproofing compounds (first revision).
• Glass fibre base coal tar pitch and bitumen felts.

4. Remedial Treatment (Clause 7.1.5)

• Guniting (sprayed mortar with mesh reinforcement) for multiple leak points.

5. Testing & Quality Control

• Final test values rounded per IS 2:1960.
• Waterproofing effectiveness verified after construction.

Typical Waterproofing Layer Sequence (Fig. 2 Sketch Summary)

graph TD
    A[Concrete Base] --> B[Waterproofing Membrane (Bitumen Felt)]
    B --> C[Protective Brick Wall]
    C --> D[Backfill]

Important Notes:

• Follow BIS codes for laying bitumen felts.
• Ensure quality and thickness of membranes as per project specs.
• Use chemical injection for crack sealing where necessary.

For detailed procedures and thicknesses, refer to IS 6494 clauses 4.4, 5.8, and 7.1.5 and related BIS specifications.

IS 6494: Workmanship and Construction Practices - Key Points

1. Concrete Placement & Compaction (Clause 5.1)

• Use properly graded aggregates and suitably designed mix.
• Concrete must be compacted thoroughly using internal vibrators.
• For inaccessible areas (e.g., walls), use slow hammering of forms to ensure compaction.
• Ensure concrete is worked around reinforcement, embedded fixtures, and corners.

2. Waterproofing Materials & Codes

• Use bitumen felts, bitumen mastic, and glass fibre reinforced bitumen as per respective IS specifications:
  • Bitumen Felts: IS code (3rd revision)
  • Bitumen Mastic: IS 5871-1970
  • Glass Fibre Reinforced Bitumen: Code of practice (2nd revision)
• Follow codes of practice for laying damp-proof treatments and in-situ waterproofing.

3. Construction Practices for Water-Tightness (Underground Reservoirs & Pools)

• Ensure water-tightness to prevent leakage and infiltration.
• Follow specified procedures and precautions during construction.
• Maintain and rectify defects as per guidelines.

Summary Table: Key Specifications

Visual: Concrete Placement Process

flowchart LR
    A[Proper Mix Design] --> B[Placement in Form]
    B --> C{Access to Area?}
    C -->|Yes| D[Use Internal Vibrator]
    C -->|No| E[Hammer Forms Slowly]
    D --> F[Compaction Around Reinforcement]
    E --> F
    F --> G[Check for Voids & Corners]
    G --> H[Waterproofing Treatment]

Note: Always refer to the latest IS codes and revisions for detailed requirements and quality control.

IS 6494: Testing After Construction of Water Retaining Structures

Key Specifications & Procedures:

• Clause 6.1:

  • Do not keep the tank dry for more than 4 weeks to avoid cracks.
  • Water arrangement for testing must be ready before last casting.
  • Testing should be done immediately after formwork removal.
  • All preliminaries (cleaning, sealing, etc.) must be completed beforehand.

• Clause 7.1.5 (Remedial Treatment Table):

  • For multiple leak points, apply Guniting:
    • Cover entire surface with mortar reinforced by mesh.
    • Use integral cement waterproofing compounds as per specifications.

Recommended Testing Steps:

1. Filling the tank with water slowly to avoid sudden hydrostatic pressure.
2. Maintain water level for at least 72 hours to detect leaks.
3. Inspect for visible leakages or dampness on walls and joints.
4. If leaks found, apply remedial treatments like guniting or bitumen mastic (IS: 5871).

Important Notes:

• Use bitumen mastic conforming to IS: 5871-1970 for waterproofing.
• Protective brick walls and damp-proofing as per Clause 5.8 and relevant IS codes should be ensured.

Summary Table: Testing Timeline

flowchart TD
    A[Formwork Removal] --> B[Water Filling]
    B --> C[Maintain Water Level ≥ 72 hrs]
    C --> D{Leakage Detected?}
    D -- Yes --> E[Apply Remedial Treatment (Guniting, Mastic)]
    D -- No --> F[Structure Approved]

This ensures early detection and correction of defects, preserving the integrity of the water retaining structure.

IS 6494 - Remedial Treatment Summary

Types of Remedial Treatments (Clause 7.1)

Key Specifications:

• Guniting (7.1.5):

  • Used when leakage occurs from many points.
  • Entire surface covered with mortar layer reinforced with mesh.
  • Thickness: As per site condition, typically 20-50 mm.

• Chemical Injection (7.1.4):

  • Suitable for severe cracks and seepage.
  • Can be applied internally without removing backfill.
  • Involves injecting waterproofing chemicals to seal cracks.

Additional Notes:

• For underground reservoirs, extra precautions are recommended to prevent sub-soil water ingress when empty (6.7).
• Integral cement waterproofing compounds should conform to BIS specifications.

Conceptual Diagram of Remedial Treatment Selection:

flowchart TD
    A[Leakage Detected] --> B{Severity of Leakage}
    B -->|Minor| C[Surface Treatment / Guniting]
    B -->|Severe| D[Chemical Injection]
    C --> E[Mortar + Mesh Layer]
    D --> F[Injection of Waterproof Chemicals]

For detailed procedures, refer to clauses 7.1.1 to 7.1.5 in IS 6494.