Distribution systems

Habari Mwanafunzi! Let's Talk Water!

Ever opened a tap in your kitchen in Nairobi, Mombasa, or even your village in Kisii and water gushes out? It feels like magic, right? But it's not magic, it's engineering! Today, we are going to pull back the curtain and explore the fascinating "highways" that bring clean, cold water right to your home. Welcome to the world of Cold Water Distribution Systems!

Think of the main water pipe from the county council as the Thika Superhighway. A distribution system is like the smaller roads and service lanes (like Jogoo Road or Waiyaki Way) that branch off to take water directly to specific estates, buildings, and finally, your tap. Let's dive in!

The Two Main 'Routes': Direct vs. Indirect Systems

Just like you can take different routes to get to town, there are two main ways to get water into a building. Understanding these is key for any plumber or technician in Kenya.

1. The Direct System

In this system, the water comes directly from the main supply line and goes straight to all the taps, toilets, and showers in the house. There's no storage tank in between.

• Pros:
  • You get water at high pressure, straight from the mains. Great for powerful showers!
  • The water is fresh as it doesn't sit in a tank.
  • Takes up less space as you don't need a large storage tank.
• Cons:
  • This is the big one for us in Kenya: If the Nairobi Water and Sewerage Company announces a water shutdown ("maji imepotea!"), you have NO water. Not a single drop.
  • Pressure can fluctuate wildly. Sometimes it's too high, sometimes it's a trickle.

        [ASCII Diagram: Direct System]

        WATER MAIN         PROPERTY BOUNDARY
        (County Council)          |
        ===================>o=====>---------------------> To Kitchen Tap
                          | |                          |
                      Stopcock |                         |
                             |                         |
                       Service Pipe                    +-----> To Bathroom Tap
                                                       |
                                                       +-----> To Toilet

2. The Indirect System

This is the system you see everywhere in Kenya! From apartments in Pipeline and Kasarani to homes in Nyali. The water from the main supply first fills up a large storage tank (we call it a cistern), usually placed on the roof. Then, gravity pushes the water from this tank down to all the taps in the house.

• Pros:
  • Water Security! When the main supply is cut off, you still have a reserve of water in your tank. This is essential for dealing with water rationing.
  • The pressure is constant and gentle because it's only determined by the height of the tank.
  • It reduces the noise of water refilling toilets as the tank fills up quietly.
• Cons:
  • The water pressure can be low, especially on the top floors of a building.
  • The storage tank needs regular cleaning to prevent contamination.
  • The tank and its supporting structure take up space and add weight to the building.

        [ASCII Diagram: Indirect System]

        WATER MAIN
        ===================>o=====>---------------------> To Roof Storage Tank (Cistern)
                          |                            /|\
                      Stopcock                          | (Gravity Feed)
                                                        |
                                                        V
                                                 +------> To Kitchen Tap (from tank)
                                                 |
                                                 +------> To Bathroom Tap (from tank)
                                                 |
                                                 +------> To Toilet (from tank)

Image Suggestion: An AI-generated, photorealistic image of a typical Kenyan urban residential building's rooftop. Show several black 'Roto' or 'Kentank' plastic water tanks of various sizes, with interconnected PVC pipes. The background should be a hazy Nairobi skyline at dawn. The image should highlight the prevalence of indirect water systems in Kenya.

The Power Behind the Flow: Understanding Pressure and 'Head'

In an indirect system, what pushes the water out of your tap? It's gravity! The height difference between the water level in the tank and your tap creates pressure. In plumbing, we call this height the "Static Head".

The rule is simple: The higher the tank, the greater the pressure.

Let's Do Some Simple Plumber's Math!

You don't need to be a math genius, but you need to know this basic principle. The pressure water exerts is directly related to its height (head). A simple and very useful rule of thumb is:

For every 10 metres of vertical height (head), you get approximately 1 bar of pressure.

Imagine you are installing a system in a 4-storey building in Ruaka. The storage tank is on the roof, and the ground floor kitchen tap is 12 metres below the tank's outlet.

    Step 1: Identify the Head
    The static head (h) = 12 metres

    Step 2: Use the Rule of Thumb
    We know that 10m head ≈ 1 bar of pressure.

    Step 3: Calculate the Pressure
    Pressure = (Total Head / 10)
    Pressure = (12m / 10)
    Pressure = 1.2 bar

    Result:
    The pressure at the ground floor kitchen tap will be approximately 1.2 bar. This is good pressure for a kitchen tap!

The Key Components of the System

A distribution system is made of several important parts. Think of them as the different parts of a car that work together.

• Service Pipe: The pipe that brings water from the county main into the plot.
• Stopcock / Gate Valve: The main "ON/OFF" switch for the water entering your house. Crucial for repairs!
• Storage Cistern: The big (usually black) plastic tank on the roof. The heart of the indirect system.
• Distribution Pipes: The network of smaller pipes (usually PVC or PPR) inside the house that carry water from the tank to the taps.
• Warning Pipe: An overflow pipe near the top of the tank to warn you if the float valve fails and the tank is about to overflow.

Image Suggestion: A clear, labeled diagram or 3D cutaway of a Kenyan house. Show the service pipe coming from the street, going to a water meter, then up to a rooftop tank. From the tank, show distribution pipes (in a different color) running down the walls to a kitchen sink, a shower, and a toilet. Label key components like 'Storage Cistern', 'Service Pipe', 'Stopcock', and 'Distribution Pipe'.

Putting It All Together: A Real-World Story

Meet Mzee Juma, who has just finished building his family home in Mtwapa, Kilifi County. The area gets its water from the county council, but the supply is not reliable; sometimes it's off for two or three days. Mzee Juma's plumber advises him to install an indirect system. They buy a 3000-litre Roto tank and place it on a strong concrete stand on his roof. Now, when the water supply is on, the tank fills up. When the supply is cut, Mzee Juma's family can still cook, clean, and shower for days using the water stored in their tank. He chose the right system for his situation!

Let's Wrap It Up!

Fantastic work today! You've learned the fundamental concepts of how water gets distributed in our homes and buildings. Remember these key takeaways:

• The Direct System is simple but unreliable during water shortages.
• The Indirect System is the most common and practical choice for Kenya, providing a crucial water reserve.
• Water pressure in an indirect system is created by gravity (head).
• The simple rule: 10 metres of head gives about 1 bar of pressure.

Next time you see those black tanks on a roof, you won't just see a tank. You'll see the heart of an indirect distribution system, working hard to make modern life possible. Well done, and keep up the great work!