Choose a well pump by the depth from the pump to the water in the driest month of the year: a suction hand pump works only to about 7 m, a rope pump or a deep-well piston pump goes much deeper, and a bucket on a rope works at any depth but exposes the water to contamination. For most community wells the rope pump is the best option, because it can be built from local materials and mended by anyone who can replace a rope or a washer.
Part of Deep Wells
Pump selection is matching a lifting device to the depth of the water, the flow the community needs, and the skills and parts available to build and repair it. A pump also seals the wellhead, which protects the water better than an open bucket.
Depth To Water Decides The Choice
Measure the depth from where the pump will sit to the water surface when the water is lowest, at the end of the dry season, not at the time you build. A pump chosen for the wet-season level may be out of reach in the dry months.
| Pump type | Max depth | Flow rate | Difficulty to build | Maintenance |
|---|---|---|---|---|
| Rope pump | 40 m and more | 10-15 L/min | Low | Easy; replace rope or washers |
| Suction hand pump | 7 m at most | 15-20 L/min | Medium | Moderate; leather seals wear |
| Deep-well piston pump | 30 m and more | 10-15 L/min | High | Moderate |
| Bucket on rope | Any depth | 5-8 L/min | None | None |
The first three can seal the wellhead with a cover (Well Protection). The bucket cannot: it brings in hands, rope and ground dirt, and a dipped bucket is how wells get contaminated (Never Dip Buckets gives the same rule for cisterns). Use a bucket only as a stopgap while you build a pump.
Why A Suction Pump Stops Near Seven Metres
A suction pump does not pull water up; it lowers the pressure in the pipe so that the weight of the atmosphere pushes water up the pipe. The atmosphere can hold up a column of water about 10.3 m high at sea level, and leaks and friction reduce what a hand pump gets to about 7 m. Below that you need a pump with the cylinder placed down in the well: the deep-well piston pump or the rope pump (Suction Pump, Deep-Well Pumps).
What You Need
- The dry-season depth to water, measured with a weighted line
- The daily volume to be lifted, from the number of users
- A list of what can be built, repaired and obtained locally: PVC pipe, rope, rubber or plastic for washers, leather, steel rod
- Someone to look after it
Method: Match Depth, Check Flow, Check Repair
Step 1: Measure the depth to the dry-season water level.
Step 2: Narrow by depth. At 7 m or less a suction pump can serve. Deeper, choose among the rope pump and the deep-well piston pump.
Step 3: Check the flow against need. Time to fill a 20 L bucket is 20 ÷ flow: at 15 L/min that is 1.33 min, or 80 s; at 5 L/min it is 4 min. A queue of users at 80 s a bucket moves much faster than at 4 min.
Step 4: Check what can be repaired. A pump nobody can mend sits idle. The rope pump is the easiest to repair, needing only rope or washers.
Step 5: Plan the sealed head. The pump should close the wellhead; the rope must pass through a cover, not leave the well open.
Worked Example: Reading The Table
A well has water at 25 m in the dry season. A suction pump is out of the question. A rope pump fits at 10-15 L/min and would be the first choice; the power needed grows with depth, so it is worth checking against the people who will turn the wheel (Rope Pump works out the effort). A deep-well piston pump also fits but is harder to build.
Common Mistakes
- Choosing by the wet-season level. The pump cannot reach the water in the dry months.
- A suction pump on a deep well. It will never prime.
- A pump nobody can repair. Parts wear out; plan for it.
- An open head. Any pump that leaves the well uncovered undoes the point of having a pump.
Safety
Moving parts and a heavy lift
Cranks, wheels and ropes trap fingers, hair and loose clothing; keep children away from pumps while they are running. Lifting a pump or its pipe out of a well is a heavy job over an open shaft: use a hoist and keep people clear of the opening.
What’s Next
- Learn next: Rope Pump — the usual choice for deeper community wells
- Combine with: Hand Pumps — building piston pumps in detail