A drip irrigation system, also called trickle irrigation, drip watering or a drip feed system, waters a crop through emitters (drip heads) fitted on drip line, drip tubing or drip hose.
Setting up a drip irrigation system: the order of design decisions
Set up drip irrigation in this order: soil survey and irrigation units, source-water analysis, filtration, number of shifts and pump duty, flushing access, then maintenance. Each step has its own section below.
Soil variation determines the irrigation units
A soil survey classifies texture and depth. Soil pits reveal profiles, with texture, depth and water-holding capacity. Similar soils can often be managed in the same irrigation shift, while lighter and heavier areas may need separate scheduling. A conversion from sprinklers to drip does not solve inherent soil problems.
Crop variety, rootstock and likely root-zone depth are design inputs, alongside emitter selection, discharge and spacing.
Water analysis and blockage risk
Test pH, iron, manganese, hardness, calcium-carbonate saturation and turbidity when assessing source water. An analysis supplies a baseline for filtration and any proposed water treatment. Some water sources create blockages in drippers. Water must also suit the crop and soil.
Blockages, component deterioration and pressure mismanagement are common faults. Maintenance has three parts: flushing the system, cleaning it (disinfestation) and monitoring its performance.
Screen, media and disc filtration
Mesh and microns describe different aspects of filtration. Mesh is the number of openings per square inch, so a higher number means smaller openings; a micron is a particle-size unit, with one thousand microns in a millimetre. The aim is to remove particles that would obstruct the emitter, while maintaining an acceptable flow, backflushing interval and water use. Finer filtration is not automatically better if it compromises delivery.
Screen filters provide surface filtration, commonly through metal, plastic or synthetic material. Their advantages can include compact installation, relatively low head loss and cost for a given flow. Media filters provide depth filtration through material such as sand or gravel; they occupy more space and generally need more backwash water. Disc filters, like media filters, provide depth filtration.
Match the filter to the emitter's smallest pathway and the source-water analysis.
Read particle and filter specifications precisely
Coarse sand, fine sand, silt and clay differ in particle diameter and mesh equivalent. Very small suspended particles can pass through a screen, whereas aggregation can create a larger obstruction downstream. A nominal screen rating therefore describes only part of the clogging risk.
Automated suction scanners can clean a screen by reversing flow locally to remove debris. Cleaning may be triggered by elapsed time or by differential pressure. Media-filter performance can deteriorate when preferential channels form through the bed and backwashing fails to lift the material sufficiently.
Peak demand and irrigation shifts
An irrigation shift is the group of units watered at the same time. The number of shifts and their required running periods must allow the whole planting to receive water during peak demand. A drip system's application rate can require longer operation than a full-cover sprinkler arrangement, so the available daily operating window matters.
Pipe material, diameter and class affect capital and running costs. Pump and motor selection must account for topography, current and future planting area and the permitted number of shifts. Extending a layout around an existing pump can reduce the ability to meet crop requirements.
Flushing the drip line: access is part of the layout
Flush mains first, then submains, then laterals. Automatic flush valves at the end of laterals have given mixed results, so remove them regularly and flush the laterals by hand.
Keep your spray records in one place. Free to start.
A flushing manifold makes flushing easier and quicker, so design it with a manageable length and pipework that is not undersized; with a manifold, open one lateral at a time. Opening too many laterals together leaves too little scouring flow, because lateral lines need a minimum velocity of 0.5 m/s to flush. If velocity is too low, open fewer laterals at once. On hydraulic valves with three-way taps, switch the valve from auto to open after opening the lateral ends: this bypasses the valve pilot and gives greater pressure for scouring, which must stay below the maximum working pressure of the drip line and fittings.
Organic matter and mineral sediment are different blockage causes. Algae and biofilm are organic matter, usually treated with an oxidising agent such as chlorine; mineral deposits are treated with acid. Deal with each separately.
Maintenance and monitoring keep performance up
Performance declines to some degree in every drip system. Regular flushing, cleaning, adequate filtration and a sound initial design keep it acceptable.
Water-source permission in England
In England, taking more than 20 m³ (20,000 litres) per day is likely to need an Environment Agency abstraction licence. The small-abstraction exemption applies to a single operation; where water is taken from several points on the same source, the combined daily volume must remain at or below 20 m³. This is the rule for England; for Scotland, Wales and Northern Ireland check the separate national guidance.
Drip tape, drip line and micro drip irrigation use the same design inputs
Whichever emitter you choose, tape or dripper, the planning inputs stay the same: water quality, soil variation, root-zone depth, number of shifts, and emitter discharge and spacing. The smallest pathway in most emitters is 500–1,000 µ, so drip systems generally need at least 120 mesh (130 µ).
Subsurface drip irrigation: drip tape buried in the root zone
Subsurface drip irrigation, also called an underground drip irrigation system, puts permanent drip tape below the ground so that it supplies water directly to the crop root zone. Water is applied within the root zone, which keeps losses down, and nothing runs off the surface. The high capital cost is the main obstacle. It is common for vegetable and tomato crops, and it may need an additional system for germination. A buried line cannot be inspected by eye, so plan its filtration and flushing from the start.
Which crops drip suits, and where micro-sprays fit
For a commercial drip irrigation system, start from the design inputs above and then choose the emitter. Drip suits vine, tree and other horticultural crops; it needs a filtration system and relatively clean water, and it allows accurate control of irrigation when it is paired with good scheduling. Micro spray irrigation (micro-sprays and mini-sprinklers) is the other low-pressure option for vines and trees. Under-canopy micro-sprinklers or drippers are a common choice for orchards.
Gravity-fed drip irrigation
A gravity-fed drip system, or any gravity-fed irrigation system, needs no pump, but it needs significant head. Drip and micro-spray systems operate at low pressure, but the filter still has to be sized for the flow it will actually receive, and the fall between tank and field has to be measured, not guessed.
Pipe, tubing and fittings for a drip system
Pipe material, diameter and class affect capital and running costs, so a PVC drip irrigation main or submain is chosen on those terms like any other pipe. Drip tubing with holes, brown or black, is chosen by the emitter's discharge and spacing. Connectors and fittings count as well: pressure must not exceed the maximum working pressure of the drip line or of fittings such as grommets, which matters when you open laterals to flush them.
Next step
Use the system and pump guide to size supply and pump duty for the layout.