Plumbing and Drainage Systems, Qualities and Pipework for SS 3

Class: SS 3
Term: First Term
Week: 4
Age: 16 years
Duration: 45 minutes
Subject: Building Construction
Topic: PLUMBING AND DRAINAGE SYSTEM
Subject Matter: Quality of good drainage; System of drainage pipe work; Description of septic tank and soakaway; Detailed drawing required
Previous Lesson: Ceilings, Parts, Materials and Functions

Specific Objectives

By the end of the lesson, pupils/students should be able to:

Cognitive Domain

• State at least five qualities of a good drainage system.
• Identify and describe different systems of drainage pipework (e.g., one-pipe, two-pipe, single stack).
• List the advantages and disadvantages of each drainage pipework system.
• Describe the purpose and components of a septic tank.
• Describe the purpose and function of a soakaway.

Affective Domain

• Appreciate the importance of well-designed and installed plumbing and drainage systems in buildings.
• Participate actively in discussions about drainage system components.

Psychomotor Domain

• Sketch simple diagrams illustrating the one-pipe, two-pipe, and single stack drainage systems.
• Draw a basic cross-section of a septic tank and soakaway.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Building Construction for Senior Secondary Schools, Book 3
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Diagrams or charts showing different drainage pipework systems (one-pipe, two-pipe, single stack).
• Illustrations of a septic tank and soakaway.
• Samples of pipes and pipe accessories (e.g., bends, junctions, traps).
• Whiteboard/Blackboard and markers/chalk.
• Textbooks on Building Construction.

Rationale for the Lesson

This lesson is important as it provides students with fundamental knowledge of plumbing and drainage systems, which are critical for the sanitation and health of building occupants. Understanding the different systems and their components helps in designing and maintaining functional and hygienic buildings. It also lays the groundwork for practical applications in the construction industry.

Prerequisite/Previous Knowledge

Students should have basic knowledge of building components and the general need for sanitation in residential and commercial structures.

Lesson Content/Board Summary

PLUMBING AND DRAINAGE SYSTEM

Qualities of a Good Drainage System

A good drainage system is essential for maintaining hygiene and preventing health hazards in buildings. Key qualities include:

1. **Durability:** The system should be made of strong, corrosion-resistant materials that can withstand continuous use and environmental factors.
2. **Efficiency:** It must effectively remove wastewater and sewage quickly without blockages or overflows.
3. **Accessibility:** All parts of the system, especially traps and inspection chambers, should be easily accessible for cleaning and maintenance.
4. **Watertightness:** All joints and pipes must be completely watertight to prevent leakage and contamination of the surrounding soil or building structure.
5. **Proper Gradient:** Pipes must be laid with an adequate slope (gradient) to ensure a self-cleansing velocity of flow, preventing solids from settling.
6. **Ventilation:** The system should be properly ventilated to prevent the build-up of foul gases and to ensure efficient flow by preventing siphonage and back-pressure in traps.
7. **Economical:** The system should be cost-effective in terms of installation, maintenance, and operation, without compromising quality.
8. **Non-absorbent:** Materials used should be non-absorbent to prevent the absorption of foul liquids and gases.

Systems of Drainage Pipework

Drainage pipework systems are designed to carry waste water and soil water away from a building. The main systems include:

1. **Two-Pipe System:**
   1. This is an older system where two separate sets of vertical pipes (stacks) are used.
   2. One stack (soil pipe) carries only foul water from water closets (WCs) and urinals.
   3. The other stack (waste pipe) carries wastewater from baths, sinks, and wash basins.
   4. Each trap is individually ventilated by a separate small pipe called an anti-siphonage pipe, connected to a main ventilating pipe.

   Advantages of Two-Pipe System:

   1. Provides excellent ventilation for all traps, reducing the risk of siphonage.
   2. Less chance of foul air entering the building due to good trap seal protection.

   Disadvantages of Two-Pipe System:

   1. Requires more pipes and fittings, making it more expensive.
   2. More complex to install and maintain due to the number of pipes.
   3. Takes up more space within the building.
2. **One-Pipe System:**
   1. In this system, all waste water and soil water from WCs, baths, sinks, and wash basins are discharged into a single vertical pipe (stack).
   2. Each trap is individually ventilated by an anti-siphonage pipe, which connects to a common ventilating pipe that runs parallel to the main stack.
   3. This system is a modification of the two-pipe system, aiming for simplicity.

   Advantages of One-Pipe System:

   1. Reduces the number of vertical pipes compared to the two-pipe system.
   2. More economical and takes up less space than the two-pipe system.
   3. Provides adequate trap ventilation.

   Disadvantages of One-Pipe System:

   1. Still requires separate ventilation pipes for each trap, adding to complexity.
   2. Risk of foul gases if ventilation is inadequate or poorly maintained.
3. **Single Stack System:**
   1. This is the most modern and simplest system.
   2. All waste water and soil water are discharged into a single vertical pipe (stack) without individual trap ventilation pipes.
   3. The traps are designed with deeper seals (e.g., 75mm deep) to resist siphonage and back-pressure.
   4. Careful design and installation are critical to prevent trap seal loss.

   Advantages of Single Stack System:

   1. Most economical due to the fewest pipes and fittings.
   2. Simplest to install and maintain.
   3. Takes up the least amount of space.
   4. Aesthetically cleaner with fewer exposed pipes.

   Disadvantages of Single Stack System:

   1. Requires very careful design, installation, and sizing of the stack to ensure proper ventilation and prevent trap seal loss.
   2. Higher risk of trap siphonage or back-pressure if not perfectly designed or if there are blockages.
   3. Not suitable for very tall buildings unless special provisions are made.

Description of Septic Tank and Soakaway

Septic tanks and soakaways are components of an on-site sewage treatment system, typically used where there is no access to a public sewer system.

1. **Septic Tank:**
   1. A septic tank is a watertight, underground chamber made of concrete, fiberglass, or plastic, through which domestic wastewater (sewage) flows for primary treatment.
   2. It serves to separate solids from liquids, store digested sludge, and allow the effluent (liquid waste) to discharge into a soakaway system.
   3. **Purpose:** To partially treat sewage by allowing solids to settle and be digested by anaerobic bacteria, reducing the volume of solids and breaking down organic matter.
   4. **Components:**
      1. **Inlet Pipe:** Carries sewage from the building into the tank.
      2. **Outlet Pipe:** Carries effluent from the tank to the soakaway.
      3. **Baffles/T-pipes:** Control the flow of sewage, prevent scum from leaving the tank, and ensure solids settle.
      4. **Scum Layer:** Lighter solids (fats, oils, grease) float to the top, forming a scum layer.
      5. **Sludge Layer:** Heavier solids settle at the bottom, forming sludge.
      6. **Effluent:** The liquid layer between the scum and sludge, which is discharged.
      7. **Access Covers:** For inspection and pumping out sludge.
2. **Soakaway (Leach Field/Drain Field):**
   1. A soakaway is a system of trenches or pits containing perforated pipes and gravel, designed to distribute the effluent from a septic tank into the surrounding soil for further treatment and absorption.
   2. **Purpose:** To safely disperse the partially treated liquid effluent from the septic tank into the ground, where it undergoes further natural purification by soil microorganisms before rejoining the groundwater.
   3. **Function:** The effluent slowly seeps through the perforated pipes into the gravel bed, then into the soil. The soil acts as a natural filter, removing remaining pollutants.
   4. **Design Considerations:**
      1. The size and design depend on the volume of effluent and the permeability (percolation rate) of the soil.
      2. Must be located away from water sources, buildings, and property boundaries.
      3. Requires a suitable soil type (not too clayey or too sandy).

Detailed Drawing Requirements for Drainage Systems

Detailed drawings are crucial for the proper planning, installation, and maintenance of plumbing and drainage systems. They typically include:

1. **Site Plan:** Showing the location of the building, septic tank, soakaway, manholes, inspection chambers, and the direction of main drains relative to property boundaries and other services.
2. **Drainage Layout Plan:** A plan view of the building showing the layout of all internal and external drainage pipes, their sizes, gradients, connections to sanitary fittings, and points of discharge.
3. **Sectional Elevation of Drainage System:** Vertical sections showing the arrangement of stacks, branches, traps, and connections to sanitary appliances, indicating pipe sizes and vertical distances.
4. **Details of Septic Tank and Soakaway:**
   1. **Plan View:** Showing dimensions, inlet/outlet positions, access covers.
   2. **Cross-Sectional View:** Showing internal dimensions, baffle walls, scum and sludge levels, inlet/outlet pipe levels, and construction materials.
   3. **Soakaway Detail:** Showing trench dimensions, perforated pipe layout, gravel bed, and covering.
5. **Schedules:** Listing pipe types, sizes, fittings, and sanitary appliances.
6. **Legends/Symbols:** Explaining all symbols used in the drawings.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Sketching, Practical Activity.

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Questioning/Activating Prior Knowledge

Teacher’s Activity: The teacher greets the students and asks them about the importance of water and waste disposal in a building. The teacher then introduces the topic: Plumbing and Drainage Systems, explaining that it covers how water comes into and leaves a building.

Pupils’ Activity: Students respond to questions about water use and waste disposal. They listen attentively to the introduction.

Learning Point: Importance of drainage

Step 2: Qualities of Good Drainage

Time: 8 minutes

Teaching Skill: Explanation/Discussion

Teacher’s Activity: The teacher explains and discusses the qualities of a good drainage system, such as durability, efficiency, watertightness, proper gradient, and ventilation, using real-life examples where possible.

Pupils’ Activity: Students listen, ask questions, and contribute to the discussion by suggesting qualities they think are important.

Learning Point: Good drainage qualities

Step 3: Systems of Drainage Pipework

Time: 10 minutes

Teaching Skill: Explanation/Demonstration/Illustration

Teacher’s Activity: The teacher introduces the three main systems of drainage pipework: Two-pipe, One-pipe, and Single Stack systems. The teacher uses diagrams or sketches on the board to illustrate each system, highlighting their structural differences.

Pupils’ Activity: Students observe the diagrams, listen to explanations, and identify the different pipework systems.

Learning Point: Drainage pipework systems

Step 4: Advantages and Disadvantages of Drainage Systems

Time: 6 minutes

Teaching Skill: Comparative Analysis/Discussion

Teacher’s Activity: The teacher leads a discussion on the advantages and disadvantages of each drainage pipework system (Two-pipe, One-pipe, Single Stack), prompting students to consider factors like cost, complexity, and efficiency.

Pupils’ Activity: Students participate in the discussion, listing the pros and cons of each system as guided by the teacher.

Learning Point: System pros and cons

Step 5: Septic Tank Description

Time: 5 minutes

Teaching Skill: Explanation/Visual Aid

Teacher’s Activity: The teacher describes a septic tank, its purpose, and main components (inlet/outlet, baffles, scum, sludge, effluent). The teacher uses a diagram to show its internal structure and function.

Pupils’ Activity: Students observe the diagram and listen to the description, understanding the role of a septic tank.

Learning Point: Septic tank components

Step 6: Soakaway Description and Drawing Requirements

Time: 3 minutes

Teaching Skill: Explanation/Instruction

Teacher’s Activity: The teacher describes the soakaway, its purpose, and how it works with the septic tank. The teacher also briefly outlines the requirements for detailed drawings of drainage systems, septic tanks, and soakaways.

Pupils’ Activity: Students listen to the description and understand the importance of drawings.

Learning Point: Soakaway function, drawing needs

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. State three qualities of a good drainage system.
2. Name two types of drainage pipework systems.
3. What is the main purpose of a septic tank?
4. Briefly describe the function of a soakaway.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Drainage system understanding

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on qualities of good drainage, systems of pipework, and septic tank/soakaway descriptions into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Recording lesson notes

Step 9: Conclusion

Time: 2 minutes

Teaching Skill: Reinforcement

Teacher’s Activity: The teacher summarises the key points of the lesson, reiterating the importance of proper plumbing and drainage for healthy living environments. The teacher encourages students to observe and identify these systems in buildings around them.

Pupils’ Activity: Students listen to the summary and reflect on the lesson.

Learning Point: Lesson consolidation

Continuous Assessment/Further Study

Type: Homework/Project

Instruction: Answer the following questions and prepare a simple sketch for one of the tasks.

1. List five qualities of a good drainage system.
2. Differentiate between the two-pipe and single stack drainage systems, stating one advantage and one disadvantage for each.
3. Draw a simple labelled sketch of a septic tank showing its main components (inlet, outlet, baffles, scum, sludge).
4. Research and write a short paragraph on the environmental impact of poorly maintained drainage systems.

Lesson Keywords

• Drainage System – Network of pipes and components for removing wastewater.
• Soil Pipe – Carries foul water from WCs and urinals.
• Waste Pipe – Carries wastewater from baths, sinks, and wash basins.
• Stack Pipe – A vertical pipe that collects and conveys discharge from branches.
• Trap – A U-shaped pipe that holds water to prevent foul gases from entering the building.
• Siphonage – Loss of water seal in a trap due to pressure changes.
• Septic Tank – An underground chamber for primary sewage treatment.
• Soakaway – A system for dispersing treated effluent into the ground.
• Effluent – Liquid waste discharged from a septic tank.
• Scum – Floating layer of light solids in a septic tank.
• Sludge – Settled heavy solids at the bottom of a septic tank.

Differentiation

For weaker learners, provide simplified diagrams and focus on identifying the main parts of each system. Allow them to work in pairs to discuss the qualities of good drainage. For faster learners, challenge them to research local regulations regarding septic tank and soakaway construction or to explore advanced drainage systems used in commercial buildings.

Suggested Lesson Videos

For further understanding, search on YouTube for:
drainage systems building construction SS3
septic tank and soakaway explained

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have clear, large diagrams or sketches of the different pipework systems, septic tanks, and soakaways. If possible, bring actual pipe samples or fittings to the class to make the lesson more practical and engaging. Begin by linking the lesson to students’ everyday experiences with plumbing. Guide the students through the qualities of good drainage, then introduce the pipework systems one by one, using the visual aids to highlight differences. Emphasise the advantages and disadvantages to foster critical thinking. When discussing septic tanks and soakaways, explain their environmental importance. Allow students sufficient time to sketch the systems as part of their learning. During note-taking, ensure students focus on key terms and definitions. Check for understanding frequently through questions and encourage students to explain concepts in their own words. Provide additional support to learners struggling with visualising the systems by offering simplified diagrams or one-on-one explanations. Encourage faster learners to think about design challenges or innovative solutions in drainage.