Explain the concept of pressure and provide four applications in plumbing. Additionally, calculate the volume of water in a tank that is 2/3 full.

The cross-sectional area is $2 \times 1.5 \text{ m}^2 = 3 \text{ m}^2$.
The height is $2.4 \text{ m}$.
Total volume of tank = Area $\times$ Height

The tank is $\frac{2}{3}$ full of water.

Since $1 \text{ m}^3 = 1000 \text{ liters}$:

2 b)

The tank is $2.4 \text{ m}$ high and $\frac{2}{3}$ full.

The formula for gauge pressure is $P_g = \rho g h$, where $\rho$ is the density of water ($1000 \text{ kg/m}^3$), $g$ is the acceleration due to gravity ($9.81 \text{ m/s}^2$), and $h$ is the height of the water.

Total pressure is the sum of atmospheric pressure ($P_{atm} \approx 101325 \text{ Pa}$) and gauge pressure.

3) An air lock is a bubble of air trapped in a pipe or plumbing system that obstructs or completely stops the flow of liquid. It is important in plumbing because air locks can prevent water from reaching fixtures, reduce the efficiency of heating systems, cause noisy pipes, and potentially damage pumps if they run dry.

4) A likely cause of leakage in plastic cisterns is material degradation due to prolonged exposure to ultraviolet (UV) radiation from sunlight or chemical attack from certain cleaning agents or water additives, which can make the plastic brittle and prone to cracking.

5 b) Required ways of controlling leakage in plastic cisterns include:

• Regular inspection: Periodically check the cistern for any signs of cracks or wear.
• Proper material selection: Use UV-stabilized plastics if the cistern is exposed to sunlight.
• Correct installation: Ensure the cistern is installed on a stable, flat surface to prevent stress points, and avoid overtightening connections.
• Pressure management: Maintain appropriate water pressure within the system to prevent excessive stress on the cistern walls.
• Prompt repair: Address any small cracks or leaks immediately using appropriate plastic repair techniques or sealants to prevent them from worsening.

6 a) Intensity of pressure is another term for pressure, which is the force exerted per unit area. In fluid mechanics, it specifically refers to the pressure at a certain point within a fluid.

6 b)

The cistern dimensions are $400 \text{ mm} \times 300 \text{ mm} \times 200 \text{ mm}$.
Assuming the height of the water is the smallest dimension, $h = 200 \text{ mm} = 0.2 \text{ m}$.

Using the formula $P = \rho g h$, where $\rho = 1000 \text{ kg/m}^3$ (density of water) and $g = 9.81 \text{ m/s}^2$.

7)

• i) Boiler core: The central part of a boiler where combustion takes place and heat is transferred to the water or other heat transfer fluid.
• ii) Patina: A thin layer that forms on the surface of metals, such as copper or bronze, due to oxidation or other chemical reactions, often providing a protective coating or a distinctive aesthetic finish.
• iii) Damper: A valve or plate used to regulate the flow of air or flue gases in a chimney, furnace, or air duct, controlling combustion or ventilation.
• iv) Flue: A duct, pipe, or channel that carries exhaust gases (like smoke or combustion byproducts) from a fireplace, furnace, water heater, or boiler to the outside atmosphere.
• v) Calorifier: A device used to heat water, typically by transferring heat from a primary heat source (like a boiler) through a coil or heat exchanger to a separate body of water for domestic or industrial use.