Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Identify different pipe materials and their uses.
• Explain water pressure, flow rate, and how to calculate pipe size.
• Describe various methods for joining pipes.
• Understand the function of fixtures like toilets and sinks.
• Explain the basics of a septic tank system.

Lesson summary

This week, we delve deeper into the essential principles of drainage, plumbing, and sanitation systems in buildings. These systems are not just about removing waste; they are critical for public health, environmental protection, and the structural integrity of buildings. Poorly designed or maintained systems can lead to water contamination, disease outbreaks, and costly damage to property. In a South African context, access to proper sanitation is a fundamental right and directly impacts the well-being of communities, especially in informal settlements and rural areas. Understanding these systems allows us to contribute to building healthier and more sustainable environments for everyone.

Lesson notes

2.1 Pipe Materials and Applications: PVC (Polyvinyl Chloride): A widely used plastic pipe, known for its affordability, durability, and resistance to corrosion. It's suitable for cold water supply, drainage, and vent systems. PVC pipes are easy to cut and join using solvent cement welding. Different classes of PVC pipe exist (e.g., Class 9, Class 12) based on pressure rating, so choosing the correct class for the application is crucial. In South Africa, PVC is commonly used in residential plumbing due to its cost-effectiveness. Consider a rural homeowner who wants to install a rainwater harvesting system. PVC pipes would be a cost-effective choice for conveying the collected rainwater to a storage tank.* Copper: A more expensive option, copper pipes are known for their durability, heat resistance, and antibacterial properties. They are used for hot and cold water supply, particularly in high-end installations or where water quality is a concern. Copper pipes are joined by soldering or compression fittings. Copper pipes are also recyclable, which aligns with sustainable building practices.

Example: A school installing a new water heating system might opt for copper pipes due to their longevity and resistance to high temperatures.* Steel (Galvanized or Stainless Steel): Steel pipes are incredibly strong and durable, making them suitable for high-pressure applications and underground installations. Galvanized steel is coated with zinc to prevent corrosion. Stainless steel offers superior corrosion resistance but is more expensive. Steel pipes are joined by threading or welding.

Example: A borehole installation in a farm setting might use galvanized steel pipes for the underground water supply due to their ability to withstand soil pressure and potential corrosion.* PEX (Cross-Linked Polyethylene): A flexible plastic pipe that offers excellent resistance to temperature fluctuations and chemicals. It's commonly used for hot and cold water supply and radiant heating systems. PEX pipes are joined using crimp fittings or expansion fittings. The flexibility of PEX makes it easier to install in confined spaces and reduces the number of fittings required.

Example: Installing underfloor heating in a new house would benefit from the flexibility and ease of installation provided by PEX pipes.* HDPE (High-Density Polyethylene): A tough and flexible plastic pipe commonly used for underground water mains and sewage lines. It is resistant to chemicals and abrasion. HDPE pipes are joined by heat fusion welding. 2.2 Water Pressure and Flow Rate: Water Pressure: The force exerted by water per unit area. Measured in kPa (kilopascals) or bar. Adequate water pressure is essential for fixtures to operate correctly. Too low pressure results in weak flow; too high pressure can damage pipes and fixtures. South African municipal water supply typically ranges from 200 kPa to 400 kPa. Pressure reducing valves (PRVs) can be used to lower pressure if it exceeds the safe limit.

Flow Rate: The volume of water that flows through a pipe per unit time. Measured in litres per minute (L/min). Each fixture requires a specific flow rate to function optimally (e.g., a shower might require 10-15 L/min).

Relationship: Water pressure and flow rate are related. Higher pressure generally leads to higher flow rate, but pipe diameter also plays a crucial role. A narrow pipe will restrict flow even with high pressure.

Calculating Pipe Diameter: Use the following formula based on flow velocity and flow rate: Q = A V, where: Q = Flow rate (m³/s) A = Cross-sectional area of the pipe (m²) V = Flow velocity (m/s) A = π (d/2)², where: d = diameter of the pipe (m)

Example Calculation: A shower requires a flow rate of 12 L/min (0.0002 m³/s). The recommended flow velocity is 1.5 m/s. What is the required pipe diameter?

Step 1: Calculate the cross-sectional area (A): A = Q / V = 0.0002 m³/s / 1.5 m/s = 0.000133 m² Step 2: Calculate the diameter (d): A = π (d/2)² => d = √(4A/π) = √(4 * 0.000133 m² / π) = 0.013 m = 13 mm.

Therefore, a 15 mm pipe would be suitable (allowing for standard pipe sizes). 2.3 Pipe Jointing Techniques: Solvent Welding: Used for PVC pipes. Involves applying a solvent cement that softens the PVC, allowing the pipe and fitting to fuse together. Creates a strong and leak-proof joint. Ensure the pipe is cut squarely and deburred before applying the solvent cement. Always use the correct solvent cement for the specific type of PVC pipe.* Compression Fittings: Used for copper, steel, and plastic pipes. Consists of a fitting body, a compression ring (olive), and a nut. Tightening the nut compresses the ring onto the pipe, creating a seal. Compression fittings are easy to install but may be prone to leaks if not properly tightened.

Example: Connecting a tap to a copper pipe using a compression fitting.* Soldering: Used for copper pipes.