DIY gravity feed uniform irrigation on sloping land using non-pressure compensating drippers
Step 1. Arrange laterals over the area to be irrigated so that each lateral follows a different contour level. The laterals may be NPC dripline or 19mm polypipe with online NPC drippers.
Step 2. Position a header tank so that the top of the tank is at least 5 metres higher than the highest lateral (let h metres be the height of the top of the tank above the highest lateral). Make sure that the header tank is fitted with a float valve or a float switch so that the header tank is always kept full.
Step 3. Subdivide the slope into zones so that the bottom of each zone is less than 0.1*h metres below the top of the zone. A zone may have many laterals.
Step 4. The top zone is irrigated by gravity feed directly from the header tank.
Step 5. For each of the other zones, use a Bermad pressure reducing valve with a yellow spring to reduce the pressure to same pressure as the top zone.
Bermad PRV Series Direct Acting Pressure Reducing Valves have been specially designed for line pressure applications that demand accurate and reliable control, regardless of fluctuations in supply pressure or flow rate. Available online from Dural Irrigation:
The discharge from each of the drippers will vary by less than 5% across the irrigated area.
If the bottom of each zone is less than 0.21*h metres below the top of the zone, then the discharge from the drippers will vary by less than 10% across the irrigated area.