Code of practice for plastic pipes work for potable water supplies, Part 1: Choice of materials and general recommendations

Scope & Key Specifications from IS 7634 Part 1 (1975)

1. Scope:

• Covers thermoplastic pipes for potable water supply:
  • Low Density Polyethylene (LDPE)
  • High Density Polyethylene (HDPE)
  • Unplasticized PVC (uPVC)
• Includes material properties, jointing methods, applications, hydraulic characteristics, handling, and storage.

2. Material Standards:

3. Relative Merits (Table 1 Highlights):

4. Hydraulic Characteristics (Clause 4.2):

• Use Hazen-Williams equation with constant C:

  • C = 140 for diameter ≤ 75 mm
  • C = 150 for diameter > 75 mm

• Equivalent pipe length for fittings:
  [ E = F \times \frac{D}{\text{cm}} ] where:

  • ( E ) = equivalent length (cm)
  • ( D ) = pipe bore (cm)
  • ( F ) = constant (see table below)

| Fitting | Constant (

IS 7634 (Part 1) - Key Formulas, Tables & Specifications for Materials

1. Materials & Relevant Standards (Clause 2.1)

2. Relative Merits of Plastics (Table 1, Clause 3.2)

3. Hydraulic Characteristics (Clause 4.2)

• Hazen-Williams constant 'C':

  • Diameter ≤ 75 mm: C = 140
  • Diameter > 75 mm: C = 150

• Frictional loss equivalent pipe length (E) for fittings:

[ E = F \times D ]

Where:

• (E) = equivalent pipe length (cm)
• (D) = pipe bore diameter (cm)
• (F) = constant from table below

IS 7634 Part 1: General Considerations - Key Formulas & Tables

1. Flow Calculation - Hazen-Williams Equation

Plastic pipes maintain flow characteristics due to corrosion resistance. Use:

[ C = \begin{cases} 140 & \text{for diameter } \leq 75 \text{ mm} \ 150 & \text{for diameter } > 75 \text{ mm} \end{cases} ]

2. Frictional Losses for Injection Moulded Plastic Fittings

Equivalent pipe length ( E ) (cm):

[ E = F \times D ]

• ( D ) = pipe bore (cm)
• ( F ) = constant depending on fitting type:

3. Material Specifications & Properties

4. Materials and Relevant IS Codes

Hydraulic Characteristics per IS 7634 Part 1 (Clause 4.2)

1. Hazen-Williams Equation for Flow Rate:

[ h_f = 10.67 \times \frac{L}{C^{1.85} \times D^{4.87}} \times Q^{1.85} ]

• C (Hazen-Williams constant):
  • 140 for pipe diameter ≤ 75 mm
  • 150 for pipe diameter > 75 mm
• (L) = length of pipe (m)
• (D) = internal diameter (m)
• (Q) = flow rate (L/s)
• (h_f) = head loss due to friction (m)

2. Equivalent Length of Fittings (to estimate frictional losses):

[ E = F \times D ]

• (E) = equivalent length (cm)
• (D) = pipe bore diameter (cm)
• (F) = constant depending on fitting type:

Notes:

• Plastic pipes resist corrosion, maintaining hydraulic characteristics over time.
• Use C = 140 for pipes ≤ 75 mm diameter, C = 150 for larger diameters in Hazen-Williams.
• Equivalent length method helps convert fitting losses into pipe length for friction loss calculations.

flowchart LR
    A[Pipe Flow] --> B[Calculate friction loss using Hazen-Williams]
    B --> C{Pipe diameter ≤ 75 mm?}
    C -- Yes --> D[C = 140]
    C -- No --> E[C = 150]
    D --> F[Calculate head loss]
    E --> F
    F --> G[Add equivalent length for fittings]
    G --> H[Total friction loss]

For detailed design, refer

IS 7634 Part 1: Handling and Storage of Plastic Pipes

Key Specifications (Clause 5.1)

• Plastic pipes are more susceptible to damage during handling and storage than metal pipes.
• Proper care must be taken to avoid abuse.
• Detailed precautions are provided in Parts II and III of IS 7634.
• Visual inspection for defects before installation is mandatory (Clause 2.2).

Hydraulic Characteristics (Clause 4.2)

• Use Hazen-Williams equation for flow calculations with constant C:

  • C = 140 for diameter ≤ 75 mm
  • C = 150 for diameter > 75 mm

• Friction loss due to fittings (Equivalent length, E in cm):

D = pipe bore in cm

Handling & Storage Best Practices

• Avoid dropping or dragging pipes.
• Store on flat, clean surfaces to prevent deformation.
• Protect from direct sunlight and extreme temperatures.
• Stack pipes horizontally with supports at intervals to prevent sagging.
• Inspect visually for cracks, warping, or damage before use.

Summary Diagram: Handling & Storage Flow

flowchart TD
    A[Receive Pipes] --> B[Visual Inspection]
    B -->|No Defects| C[Store on Flat Surface]
    B -->|Defects Found| D[Reject or Repair]
    C --> E[Protect from Sunlight & Heat]
    E --> F[Stack Horizontally with Supports]
    F --> G[Handle Carefully to Avoid Damage]

This concise guide aligns with IS 7634 Part 1 provisions and practical engineering practice for pipe longevity and performance.

IS 7634 Part 1: Laying and Jointing - Key Points

1. Laying and Jointing (Clause 6.1)

• Specific techniques differ from metal pipes.
• Detailed procedures are in:
  • Part II: Polyethylene (PE) pipes
  • Part III: Unplasticized PVC pipes

2. Hydraulic Characteristics (Clause 4.2)

• Use Hazen-Williams equation for flow rate calculations:

  [ h_f = 10.67 \times \frac{L}{C^{1.85} \times D^{4.87}} \times Q^{1.85} ]

  Where:

  • (h_f) = head loss (m)
  • (L) = pipe length (m)
  • (C) = Hazen-Williams coefficient:
    • 140 for diameter ≤ 75 mm
    • 150 for diameter > 75 mm
  • (D) = pipe diameter (m)
  • (Q) = flow rate (m³/s)

3. Equivalent Length of Fittings (Friction Loss)

• Equivalent length (E) in cm:

  [ E = \frac{F}{D} ]

  Where:

  • (F) = constant for fitting type
  • (D) = pipe bore in cm

4. Handling & Storage (Clause 5.1)

• Plastic pipes are more prone to damage; handle with care.
• Avoid abuse during transport and storage.
• Refer to Parts II & III for detailed precautions.

flowchart TD
    A[Laying & Jointing] --> B[Part II: PE Pipes]
    A --> C[Part III

IS 7634 Part 1 (1975) — Testing of Installations: Key Points

1. Testing Procedure (Clause 7.4)

• Fully charge the system with water, displacing air.
• Close air vents, inspect joints for seepage and check supports.
• Apply test pressure gradually until required pressure is reached.
• Note: Thermoplastic pipes (PE, PVC) expand initially, causing pressure drop even without leakage.

2. Make-up Water for Testing Thermoplastic Pipes

• Extra water needed to compensate for pipe expansion during pressure build-up.
• Test duration: 1 hour; pressure drop should not exceed 0.2 kg/cm².
• Time to reach steady pressure: approx. 12 hours.

3. Make-Up Water Quantities

Summary Diagram: Testing Process Flow

flowchart TD
    A[Charge system with water] --> B[Displace air & close vents]
    B --> C[Inspect joints & supports]
    C --> D[Apply test pressure gradually]
    D --> E{Pressure steady after 12 hrs?}
    E -->|Yes| F[Check pressure drop ≤ 0.2 kg/cm² in 1 hr]
    E -->|No| G[Add make-up water as per table]
    G --> D
    F --> H{Leakage?}
   

Effect on Water Quality - IS 7634 Part 1 (Clause 7.5 & 8.1)

1. Water Quality Impact:

• Properly manufactured plastic pipes cause no taste or odor problems.
• Safe from a bacteriological standpoint (refer IS: 3076-1968, IS: 4984-1972, IS: 4985-1968).
• New PVC pipes must be flushed with fresh water for ~1 hour to remove lead residues from extrusion stabilizers.

2. Hydraulic Characteristics (Clause 4.2):

For flow calculations, use Hazen-Williams equation with:

Frictional loss from fittings:

[ E = \frac{F \times D}{100} \quad \text{(Equivalent pipe length in cm)} ]

3. Material Merits Affecting Water Quality (Clause 3.2, Table I):