Design a water network on paper before laying any pipe: draw a map of the source, tank, houses and tap points, survey the heights between them, and work out the daily demand, then choose a layout and pipe sizes that leave at least 0.5 bar (5 m of head) at every tap. For 5-30 people a branched layout is usually fine, and the plan should leave room to add loops later.
Part of Water Distribution
Network design is the planning stage of a water supply: where the water comes from, where it is stored, which route the pipes follow, how large they are and where the valves and taps go. Mistakes made here are expensive to fix once the pipes are buried.
The Map Comes Before The Pipe
A network is a set of heights and distances. Water runs only downhill (or under pressure from a higher tank), so the first job is to know which points are higher than which, and by how much. A good map shows:
- the source and the likely tank site
- every house or tap point, and the distance along the ground between them
- the height of each point above the lowest one
- obstacles: streams, rock, roads, steep banks
- anything that could contaminate the water: latrines, animal pens, waste
Heights come from a level (A-Frame Level) or from the gradient methods in Gradient Calculation.
What You Need
- A sketch plan or drawn map with a scale
- A level and a measuring tape or rod
- A figure for daily demand per person — at least 20 L per person per day, and 50–80 L for a comfortable community with laundry and a garden (Community Water System)
- The dry-season flow of the source, measured, not estimated
Method: Map, Measure, Choose, Check
Step 1: Map the sites and measure the distances.
Step 2: Measure the heights from the source and tank down to each tap.
Step 3: Work out demand. People × litres per person per day.
Step 4: Choose the layout (Branched vs. Looped).
Step 5: Size the pipes section by section (Pipe Sizing).
Step 6: Add the fittings: isolation valves, air valves at high points, drain points at low points, and a storage tank.
Step 7: Check pressure at both ends. Every tap needs at least 0.5 bar (5 m of head) at peak flow, and no pipe should see more than 6 bar (60 m); where it does, add break pressure tanks.
Worked Example
A hamlet of 6 households. At an assumed 5 people per household, that is 30 people. Demand: 30 × 20 L = 600 L/day at the minimum, or 30 × 50 L = 1,500 L/day for comfort. One day’s storage is therefore 1,500 L, and a tank of 2,000–5,000 L gives a comfortable buffer. Six households fit one standpipe at the rate of 5–8 households per standpipe, provided every house is within 200 m of it. A branched layout from the tank to that one standpipe is enough, with room for a second branch later.
Common Mistakes
- Laying pipe before surveying. An unexpected rise in the route traps air or kills the flow.
- Designing for the average, not the peak. See Pipe Sizing.
- Forgetting valves, drains and air release. They are cheap to plan and expensive to add later.
- Running a non-potable line beside the drinking-water pipe. A cross-connection can contaminate the whole network.
Safety
Test with water, never with air
New lines carry up to 6 bar. Fill them slowly from the top with the air bled out, and never pressure-test with compressed air, which can shatter plastic pipe and throw fragments. Keep drinking-water pipes physically separate from any non-potable line.
What’s Next
- Learn next: Branched vs. Looped — the first design choice
- Combine with: Distribution Network — peak demand factors and ring mains in detail