Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

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Performance objectives

• Identify common building services and their symbols.
• Draw and interpret symbols for plumbing and electrical fixtures.
• Detail basic water supply and drainage systems on a plan.
• Represent electrical layouts on a simple plan.
• Explain the importance of coordinating different construction drawings.

Lesson summary

This week, we delve into the crucial area of building services and their representation in civil drawings. Building services are the systems within a building that make it habitable and functional. This includes water supply, drainage, electrical systems, and ventilation. Accurately representing these services in civil drawings is vital for coordination during construction, preventing costly errors, and ensuring the building operates efficiently and safely. Imagine trying to build a house in Soweto without clearly planned water pipes - you could end up digging up floors later! Or a school in Durban without considering proper ventilation – the classrooms would be unbearable in summer.

Lesson notes

2. 1. Building Services Overview Building services encompass all the systems within a building that contribute to its functionality and habitability.

We'll focus on four main areas: Water Supply: This system delivers potable (drinkable) water to various fixtures within the building, such as taps, toilets, showers, and washing machines. It includes pipes, valves, meters, and sometimes a water storage tank (especially important in areas with unreliable water supply).

Drainage: This system removes wastewater (both greywater from sinks and showers, and blackwater from toilets) from the building and directs it to the municipal sewer system or a septic tank. It consists of pipes, traps (to prevent sewer gases from entering the building), vents (to allow air into the system and prevent siphoning), and inspection chambers.

Electrical: This system provides electrical power for lighting, appliances, and other electrical equipment. It includes cables, conduits, switches, outlets, distribution boards (DBs), and earthing systems. All electrical installations must comply with SANS 10142, the South African National Standard for electrical installations.

Ventilation: This system provides fresh air to the building and removes stale air, preventing the buildup of moisture and pollutants. It can be natural (e.g., windows and vents) or mechanical (e.g., fans and air conditioning systems). 2.

2. Symbols and Conventions Each building service is represented by specific symbols on civil drawings. These symbols are standardized to ensure clear communication between designers, contractors, and plumbers/electricians. Here are some common examples (ensure these are accurately drawn and easily distinguishable in your own drawings): Water Supply: Cold Water Tap: Circle with 'C' inside Hot Water Tap: Circle with 'H' inside Water Meter: Rectangle with 'WM' inside Gate Valve: Two opposing triangles touching at their points.

Drainage: Toilet: Stylized representation of a toilet bowl (oval with a smaller circle inside)

Sink: Rectangle with a drain symbol (small circle with a cross)

Inspection Chamber: Circle with a line through it.

Drain Pipe: Dashed line.

Electrical: Single Light Switch: Small circle with a line extending from it.

Double Light Switch: Small circle with two lines extending from it.

Plug Point (Single): Rectangle with a dot in the center.

Plug Point (Double): Two rectangles side-by-side, each with a dot in the center.

Light Fitting: Circle with a cross inside.

Distribution Board (DB): Rectangle with 'DB' inside.

Ventilation: Air Vent: Rectangle with angled lines inside.

Fan: Circle with blades represented inside. It's crucial to learn these symbols by heart and practice drawing them accurately. 2.

3. Detailing Water Supply and Drainage Systems Let's consider a simple example: detailing the water supply and drainage for a single bathroom in a house in Khayelitsha.

Example 1: Bathroom Plumbing Layout Imagine a small bathroom with a toilet, sink, and shower. The cold water supply enters the bathroom from a main supply line (usually located outside the bathroom).

Cold Water Supply: The cold water pipe (represented as a solid line on the drawing) runs to the toilet (for flushing), the sink (for washing hands), and the shower. Each fixture requires a stop valve (gate valve) near the fixture for maintenance purposes. These stop valves are drawn using their respective symbols. The pipe size will depend on the water pressure and the number of fixtures, but a common size is 15mm.

Hot Water Supply: The hot water pipe (also a solid line) comes from the geyser (hot water heater, which is typically located outside the bathroom). It runs only to the sink and the shower, also with stop valves near each fixture. The pipe size is typically 15mm.

Drainage: The toilet, sink, and shower each have a drainpipe that connects to a main drain line (represented as a dashed line). Each drainpipe needs a P-trap (a curved pipe that holds water, preventing sewer gases from entering the bathroom). These traps must be shown. The main drain line slopes slightly (typically 1:50) towards the connection to the main sewer line outside the house. A vent pipe is also needed to prevent siphoning. The diameter of the drain pipes will vary; a toilet drain is typically 110mm, while sink and shower drains are typically 50mm. Crucially, the drawing MUST show: All pipes, including their type (cold water, hot water, drain, vent). All fixtures (toilet, sink, shower). All valves and traps. Pipe sizes. A scale bar. Annotations labeling each component. 2.

4. Detailing Electrical Wiring Now, let’s look at detailing the electrical wiring for the same bathroom.

Example 2: Bathroom Electrical Layout The bathroom needs lighting, a switch for the light, and possibly a plug point for a hairdryer or shaver.

Power Supply: The power supply comes from the distribution board (DB). A circuit breaker in the DB protects the bathroom circuit.