A gravity water main for a settlement should reach every zone with at least 1-2 m of residual head at each tap and no more than 30 m of pressure head at any, which fixes how high the reservoir may sit above the lowest user. Route the main along paths for access, avoid summits where air collects, keep it away from latrines and animal pens, and add an isolating valve at each cluster.
Part of Settlement Layout for 150 People
Water distribution routes are the planned paths of pipes and open channels that carry water from source and storage to the communal point, houses, barns, workshops and fire points.
The Route Is Set By Height, Not By Distance
The layout guide wants the gravity-fed plumbing system to reach every zone: a communal water point at the core, livestock water piped to barn troughs, workshop water for forge and pottery, and fire-fighting points (Gravity-Fed Plumbing). The design limits come from the distribution guide (Distribution Network):
- Place the service reservoir 10-20 m above the highest user.
- Leave at least 1-2 m of residual pressure head at every tap; below 1 m it barely trickles.
- More than 30 m stresses joints.
- Route to avoid high points that trap air; use a ring main where one section must be repairable with the rest live.
- Trenches at least 450 mm deep; test joints before backfilling.
Worked Example: Is A Break Tank Needed?
Inputs: the settlement’s ground drops 20 m from its highest house to its lowest; the reservoir is placed 15 m above the highest tap (within 10-20 m); 1 m of water head is 9.81 kPa, about 0.098 bar.
- Head at the highest tap, with no flow: 15 m.
- Head at the lowest tap: 15 + 20 = 35 m.
- Compare with the 30 m joint limit: 35 m is over it by 5 m.
- In bar: 35 × 0.098 ≈ 3.4 bar at the lowest tap.
So the lowest houses exceed the guide’s limit, and the settlement needs a second pressure zone or a break-pressure tank to cut the head for the low section (Pressure Zones). That guide allows up to 6 bar (60 m) in a zone, twice the distribution guide’s 30 m joint-stress limit used here; this article keeps the stricter figure. Lowering the reservoir would bring the lowest tap under 30 m (5 m above the highest tap gives 5 + 20 = 25 m), but the guide’s 10-20 m is the preferred height and a low reservoir leaves little head to cover friction losses at the highest tap during peak flow. A break-pressure tank for the low section is the safer fix.
Flow is a separate check: 150 people at the guide’s basic 30 L per person a day is 4,500 L a day, or 4,500 ÷ 86,400 ≈ 0.052 L/s on average, and at the 2.5-3× peak factor 0.13-0.16 L/s. A 50 mm main that carries about 1.0 L/s is far above this; the limit is the head, not the pipe.
Method: Lay The Route
Step 1: Mark the source, reservoir and highest tap on the contour map and compute head at the lowest tap as above.
Step 2: Run the main along primary paths so a leak is seen and a repair crew can reach it, but not under cart routes at the minimum depth; cross them deeper or in a sleeve.
Step 3: Keep clear of sanitation. Water mains and latrines or composting areas should not share a trench; separate them by the distances in Source Protection.
Step 4: Put an isolating valve at each cluster and at each zone branch, and mark them on the plan.
Step 5: Place fire points where the head gives usable flow, and a drain at the lowest point of every run.
Common Mistakes
- Ignoring a summit — air collects and stops flow.
- A trough fed by an open end below its rim — contamination can siphon back; keep the supply above the water surface.
- Closing valves fast — water hammer cracks pipe; the distribution guide says to take 30 seconds or more.
Safety
Pressure and trenches
A joint that fails at 35 m of head sprays and floods a trench. Test joints before backfill, and shore any trench deeper than a person’s knees: collapsing walls kill. Never connect a drinking main to a trough, tank or pipe that has held anything but treated water.
What’s Next
- Learn next: Water Points for Fire Fighting — using the same system for fire
- Combine with: Infrastructure Scalability — sizing for growth