Deep Wells
Why This Matters
Surface water is unreliable — it dries up in drought, floods in rain, and carries every pathogen upstream. Groundwater from a properly constructed deep well is available year-round, naturally filtered through meters of soil, and far less vulnerable to contamination. For a permanent settlement, a good well is worth more than almost any other infrastructure.
Assessing the Water Table
Before you dig or drill anything, figure out where the water is and how deep.
Terrain clues:
- Valley bottoms and low-lying areas have shallower water tables than hilltops
- Near rivers and streams, the water table is usually within 3-10m
- Areas with lush green vegetation in dry season often indicate shallow groundwater
- Willows, cottonwoods, and reeds are strong water indicators
Test holes: Dig or auger a narrow test hole (10-15cm diameter) to check depth to water. This is far cheaper in effort than committing to a full well in the wrong spot. Dig at least 3 test holes in different locations before choosing your well site.
Tip
Talk to anyone who’s lived in the area. Local knowledge of existing wells, seasonal water levels, and dry spots is worth more than any technique.
Site selection rules:
- Minimum 30m from any latrine, animal pen, or waste disposal area
- Uphill from contamination sources
- Accessible to the community (not on someone’s private land if it’s communal)
- On stable ground, not on a slope prone to erosion
Hand-Dug Wells (to ~20m)
A hand-dug well is a large-diameter hole (1-1.5m across) lined with brick, stone, or concrete rings. It’s labor-intensive but requires no specialized equipment.
Warning
Hand-dug wells are dangerous. Cave-ins kill people every year. Never dig without shoring or lining. Never work alone — always have someone at the surface. If you smell rotten eggs or feel dizzy, get out immediately — toxic gases accumulate in deep holes.
Step 1 — Mark out a circle 1.2-1.5m in diameter. Begin digging with picks and shovels. Haul spoil up with a bucket on a rope and a tripod with a pulley.
Step 2 — Line the walls as you go. The safest method is sinking concrete rings: pre-cast rings (1m diameter, 0.5m tall, 5-8cm thick) are placed on the surface. You dig underneath, and the rings sink under their own weight. Add new rings on top as you go deeper.
Step 3 — When you hit water, keep digging into the saturated zone at least 2-3m to ensure adequate storage volume in the well. You’ll need to bail water continuously while digging this section.
Step 4 — Install a concrete surface seal: a solid concrete apron (3m diameter, 10cm thick) around the wellhead, sloping away to drain surface water. The top 3m of well lining must be sealed watertight (plastered with cement mortar) to prevent surface water seeping in.
Percussion (Cable Tool) Drilling (to 30m+)
For depths beyond what’s practical to hand-dig, percussion drilling punches through soil and rock using a heavy metal bit dropped repeatedly.
Building the rig:
- Tripod: 3 poles, each 5-6m long, lashed at the top
- Pulley at the apex
- Rope: strong manila or synthetic rope, 6-10mm
- Drill bit: a heavy steel chisel point, 30-50kg, with a narrow diameter (10-15cm)
- Bailer: a pipe with a check valve at the bottom for scooping out cuttings
Process:
- Raise the bit 1-2m using the rope and pulley
- Drop it. The impact fractures soil and rock
- Every 30-50 drops, pull the bit and lower the bailer to scoop out loosened material
- Add water to the hole if drilling dry — it helps carry cuttings into the bailer
- When you pass through unstable layers (sand, loose gravel), insert casing immediately to prevent collapse
Rates: Expect 1-3 meters per day in soft soil, much less in rock. A 20m well might take 1-3 weeks.
Augering (to 25m in soft ground)
A hand auger is a large drill bit turned by hand using a T-handle. Fastest method in clay and soft soils.
Equipment:
- Bucket auger (for clay) or spiral auger (for mixed soils)
- Extension rods: steel pipe sections that screw together, each 1-1.5m long
- T-handle: a crossbar for turning
Process:
- Turn the auger clockwise until it fills with soil
- Pull it up, empty it, repeat
- Add extension rods as you go deeper
- When you hit water-bearing sand, switch to a bailer — augers don’t work well in saturated sand
Tip
Two people turning the T-handle makes augering significantly faster and less exhausting. Rotate teams every 15-20 minutes.
Well Casing and Screens
Every borehole needs casing (solid pipe) through the upper layers and a screen (slotted pipe) in the water-bearing zone.
Casing: PVC pipe (110-160mm diameter) is ideal. It’s light, cheap, and doesn’t corrode. Join sections with PVC solvent cement.
Screen: Cut slots in the PVC casing using a hacksaw. Slots should be 0.5-1mm wide, 50mm long, in rows spaced 10mm apart. Cover the slotted section with fine mesh or a nylon sock to keep fine sand out.
Gravel pack: After lowering the casing and screen into the borehole, fill the space between the casing and the borehole wall with clean, washed gravel (3-6mm) around the screen section. Above the screen, backfill with clay or cement to seal.
Pump Selection
| Pump Type | Max Depth | Flow Rate | Difficulty to Build | Maintenance |
|---|---|---|---|---|
| Rope pump | 40m+ | 10-15 L/min | Low | Easy — replace rope/washers |
| Suction hand pump | 7m max | 15-20 L/min | Medium | Moderate — leather seals wear |
| Deep-well piston pump | 30m+ | 10-15 L/min | High | Moderate |
| Bucket on rope | Any depth | 5-8 L/min | None | None |
The rope pump is the best option for most community wells. It’s a continuous loop of rope with rubber or plastic washers spaced 1m apart, running through a PVC pipe submerged in the well. Turning a wheel at the top pulls water up continuously. It can be built entirely from local materials plus some PVC pipe.
Common Mistakes
| Mistake | Consequence | Prevention |
|---|---|---|
| No surface seal | Surface runoff contaminates the well | 3m concrete apron + sealed upper casing |
| Well too close to latrine | Fecal contamination of groundwater | Minimum 30m separation, well uphill |
| Digging without shoring | Cave-in, injury or death | Line walls as you dig, never work alone |
| Screen slots too wide | Sand enters well, clogs pump | Slots no wider than 1mm, use gravel pack |
| Not developing the well | Low yield, cloudy water | Pump vigorously for several hours after completing to clear fine particles |
What’s Next
- Community Water System — connecting your well to a distribution network
- Community Water Testing — verifying your well water is safe
- Cisterns and Rainwater Storage — supplementary storage