epi

An epi is a single lateral drip irrigation tube, typically polyethylene, laid along a crop row to deliver water directly to soil at low pressure. The term is colloquial shorthand used by irrigators and growers, especially in horticulture and high-value field crops where water placement matters. Each epi is punctured or fitted with emitters spaced 30 to 60 centimetres apart, allowing water to seep slowly into the root zone rather than spray overhead.

Epis are most common in nurseries, vineyards, berry fields, and vegetable production. They connect to a main header line and typically operate at 5 to 20 pounds per square inch. The tubes themselves are thin-walled, usually 12 to 16 millimetres in diameter, and cheap enough that growers often replace them annually. Because water flows close to the plant base with minimal runoff or evaporation, epi systems use 30 to 50 percent less water than sprinkler or flood irrigation over the same area.

Common failures and maintenance

Epis clog easily. Sediment, algae, and mineral deposits accumulate in the small emitter passages, cutting flow to individual plants or blocking entire sections. Grit in the water supply is the usual culprit; proper filtration (150 mesh or finer) at the pump station helps, but even then regular flushing is necessary. When an epi stops working mid-season, growers must walk the row, find the blockage, and clear or replace the line, a labour-intensive task in large fields.

Rodents and UV damage also shorten epi life. Rabbits and voles chew through tubes left exposed on the soil surface. Sunlight degrades the plastic over one to three seasons, making it brittle and prone to fracture. Many growers lay epis under mulch or black plastic to extend their working life and reduce weeding.

The term "epi" appears to derive from the early trademark or product name for drip emitter lines in Australian and New Zealand horticulture, where the technology was adopted widely in the 1970s and 1980s. It has stuck as colloquial shorthand in those regions and increasingly among irrigators elsewhere, though technical manuals and equipment suppliers often use the more formal terms drip line, lateral line, or drip tape.