Pipe a spring to the community by running a buried pipe from the box outlet down to a storage tank, sized so friction leaves at least 0.5 bar at the end: 10 L/min through 600 m of 25 mm pipe on a 20 m fall loses 4.3 m of head to friction and still arrives at about 1.6 bar. Bury the pipe, put an air release at every high point and a valve at the box, and store the flow in a tank, because a spring runs all day while people draw water in peaks.
Part of Spring Capture
Piping from a spring is the gravity line that carries the captured water to a tank or a standpipe in the settlement. It costs nothing to run, but it must be sized, buried and vented properly to deliver the spring’s flow.
A Spring Above The Settlement Needs No Pump
The height of the spring above the taps is the whole driving force. Ten metres of height gives about 1 bar, and the pressure at the lowest point of the line is 9.81 kPa per metre of drop. A fall of 20 m gives 9.81 × 20 = 196 kPa, 1.96 bar, when no water is flowing. Friction in the pipe uses part of that head while water flows; what is left is the pressure at the end. The water must still arrive with at least 0.5 bar (5 m) at each tap, and no section may exceed 6 bar (60 m); beyond that, put in break pressure tanks (Break Pressure Tanks). Pipe Sizing sets out the method (Pipe Sizing).
Worked Example: A Spring Line
The spring gives 20 L in 2 minutes, 10 L/min, which is 10 ÷ 60,000 = 1.67×10⁻⁴ m³/s or 0.167 L/s. The pipe runs 600 m and the end is 20 m below the box.
Use the Hazen-Williams equation from Pipe Sizing, h = 10.67 × L × Q^1.852 ÷ (C^1.852 × d^4.87), with C = 140, for a 25 mm bore:
- Loss per 100 m = 10.67 × 100 × (1.67×10⁻⁴)^1.852 ÷ (140^1.852 × 0.025^4.87) = 0.72 m
- Loss over 600 m = 6 × 0.72 = 4.3 m
- Head left at the end = 20 − 4.3 = 15.7 m, which is 1.6 bar; the 0.5 bar needed at a tap is met, with 10.7 m to spare
- Speed = flow ÷ area = 1.67×10⁻⁴ ÷ (π ÷ 4 × 0.025²) = 0.34 m/s
A 32 mm pipe would lose only 0.22 m per 100 m, but the 25 mm pipe is already enough and cheaper. The speed is slow, so silt in the water settles in the pipe: keep the box outlet clear of sediment (Outlet & Overflow) and fit a drain at low points (Drain Points).
Store The Flow: The Spring Runs All Day, Use Comes In Peaks
At 10 L/min the spring delivers 10 × 1,440 = 14,400 L a day. Most of it is wanted in the daytime. If the community draws water over 12 hours, the other 12 hours of flow, 10 × 60 × 12 = 7,200 L, would run to waste without a tank. A tank sized for at least one full day of the supply, as the storage guide advises, holds 14,400 L (Storage Tanks, Tank Sizing).
What You Need
- Pipe, of a size from the calculation (Pipe Making, Metal Pipes, Clay Pipes for materials)
- A survey of the route — heights along it, with a water tube level or other level (Water Tube Level)
- A shut-off valve at the box and air-release fittings at every high point (Air Valves)
- A tank at the end (Storage Tanks)
- A trench to depth (Burial Depth)
Method: Survey, Size, Bury, Fill, Test
Step 1: Survey the route and mark the highest points between the box and the tank. A line that rises over a ridge collects air there, and the head must be enough to carry water over it (Air Locks).
Step 2: Size the pipe by the head budget as above: friction loss no more than the drop minus 5 m.
Step 3: Dig the trench deep enough to protect the pipe from frost, sun and knocks, and keep the route away from latrines, drains and ground that floods.
Step 4: Lay the pipe on a smooth bed, joint it carefully, and fit air-release fittings at every crest and drain points at low spots.
Step 5: Fill slowly from the top, bleeding air at each crest until water, not air, comes out.
Step 6: Flush and disinfect before use, and test the water at the tap (Community Water Testing).
Common Mistakes
- Ignoring high points. Air collects and the flow stops.
- Sizing by the daily volume. The line must carry the flow the spring gives and the tank’s draw.
- No valve at the box. A repair then drains the whole line.
- A shallow pipe. It freezes, cracks and warms in the sun.
- A route past a latrine or drain. A leak draws in contamination when the pressure drops.
Safety
Pressure and trenches
A pressurised line can burst and blow fittings: test with water after bleeding the air, never with compressed air. Trenches deeper than 1.2 m need sloped or shored walls and spoil at least 0.6 m from the edge.
What’s Next
- Learn next: Air Locks — preventing and clearing air in the line
- Combine with: Community Water System — distributing the water to the settlement