Introduction
A growing number of Kenyan smallholder tomato farmers use gravity — not an electric or petrol pump — to run their drip irrigation system, drawing water from a tank mounted on a raised stand. This article sets out a practical layout and equipment list for irrigating 1 acre (≈4,000 m²) of tomatoes using dripline, with the tank positioned on a 2-metre stand and pressure supplied entirely by gravity (height/elevation pressure).
The Pressure Reality of a 2-Metre Stand
A 2-metre water column produces roughly 0.2 bar (≈2.9 psi) of static pressure at the tank outlet — before any losses from pipe friction, fittings, or the filter are subtracted. This is well below the 1.0 bar that many drip systems are designed around, so the layout below is built specifically to work within this constraint, rather than assuming a booster pump will compensate later. Two design principles follow directly from this:
- Short lateral runs. Every dripline lateral is kept to roughly 20–25 metres so friction loss does not consume the limited available head.
- Zoned, sequential irrigation. The 1-acre plot is split into four irrigation zones of about 0.25 acre each, opened one at a time via valves. Concentrating the full (small) head on one zone at a time gives usable flow and wetting; opening the whole acre simultaneously would starve the far end of every line.
Field Layout
Plot dimensions: 50 m × 80 m (4,000 m², ≈0.99 acre)
Zoning: 4 zones of 50 m × 20 m (≈0.25 acre each)
Tomato spacing: rows 1.0 m apart, dripline row length 20 m per zone → 50 rows per zone (200 rows total)
Emitter spacing: 30 cm along the dripline, matching typical in-row tomato plant spacing
TANK (on 2m stand)
|
[Filter + Valve]
|
MAINLINE (63mm HDPE)
|
---- Distribution Manifold ----
/ | | Zone 1 Zone 2 Zone 3 Zone 4
(50m x 20m) (50m x 20m)(50m x 20m) (50m x 20m)
50 rows of 50 rows of 50 rows of 50 rows of
20m dripline 20m dripline 20m dripline 20m dripline
(1m apart) (1m apart) (1m apart) (1m apart)Each zone has its own 32mm header pipe running along the 50 m width, feeding the 50 dripline laterals for that zone. A ball valve at each zone inlet allows the farmer to irrigate one zone at a time, cycling through all four in a single watering session.
Equipment List (AFRODRIP Products)
All items below — except the storage tank itself — are AFRODRIP-manufactured HDPE pipe, dripline, and PP compression fittings.
| Component | Specification | Approx. Quantity | Function |
|---|---|---|---|
| HDPE Mainline Pipe | DN63mm, PN6 | ~20–30 m | Carries water from tank stand to the distribution manifold |
| HDPE Sub-main Pipe | DN40mm, PN6 | ~100–150 m | Connects manifold to each of the 4 zone headers |
| HDPE Header Pipe | DN32mm, PN6 | 4 × 50 m = 200 m | Distributes water along each zone, feeding the dripline laterals |
| Dripline | 16mm, non-pressure-compensating, 1.0–1.6 LPH emitters, 30cm spacing | ~4,000 m total (200 laterals × 20 m) | Delivers water directly to the tomato root zone |
| PP Male Adaptor | 63mm | 1 | Connects tank outlet fitting to the HDPE mainline |
| PP Reducing Tee | 63mm × 40mm | 1 | Splits mainline into sub-main at the manifold |
| PP Tee | 40mm × 32mm | 4 | Connects sub-main to each zone's header pipe |
| PP Elbow | 63mm / 40mm as needed | 2–4 | Direction changes in mainline/sub-main routing |
| PP End Cap | 32mm | 4–8 | Closes header pipe ends |
| Dripline Start/Take-off Connector | 16mm | 200 | Connects each dripline lateral to the header pipe |
| Dripline End Cap/Closure | 16mm | 200 | Closes the far end of each dripline lateral |
| Screen or Disc Filter | 63mm inline, 120-mesh | 1 | Fitted immediately after the tank outlet, before the mainline, to prevent emitter clogging |
| Ball Valve | 40mm, one per zone | 4 | Enables sequential, zone-by-zone irrigation to concentrate available gravity pressure |
Note: the filter and ball valves are essential control-head components. If a specific model is not held in AFRODRIP's standard catalogue, they should be confirmed with AFRODRIP's sales team or sourced as a compatible add-on, since reliable filtration is mandatory for any gravity-fed dripline system regardless of pressure source.
Practical Recommendations
- Position the tank stand at the field's centre-edge, not a far corner, to minimise mainline length and preserve head.
- Filter before the mainline, not after — install the screen/disc filter directly at the tank outlet so no unfiltered water ever reaches the 63mm mainline or the 16mm dripline.
- Irrigate one zone at a time. With only ~0.2 bar available, running all four zones together will under-deliver water to the zones farthest from the tank.
- Choose non-pressure-compensating dripline rated for low-head operation; pressure-compensating dripline typically requires more head than a 2-metre stand can supply and will underperform here.
- If yields or plot size grow, raise the stand. A 2.5–3 m stand roughly doubles available head, meaningfully easing zone sizing and lateral length limits for future seasons.
Conclusion
A 2-metre gravity stand can reliably irrigate 1 acre of tomatoes on AFRODRIP dripline, provided the system is zoned into short, sequentially-irrigated sections rather than run as a single continuous network. Careful pipe sizing, proper filtration at the tank outlet, and disciplined zone-by-zone operation are what make a low-pressure gravity system work in practice on a Kenyan smallholding.
Prepared as a technical irrigation layout reference for AFRODRIP Limited customers.