Irrigation Pipes

The pipe hierarchy

A drip system has three pipe roles, in descending size: the mainline (from the head across the farm's length, carrying the full or a large share of the flow), the submains (from the mainline to the blocks/rows, carrying a block's flow), and the laterals/drip lines (to the crop — the drip lines and drip tape themselves). Each level is sized by the flow it carries and the distance it carries it.

Materials

How pipe size is actually decided

Two constraints, one answer. First, velocity: pipe too small for the flow and the water moves fast — pressure is lost to friction along the run, the far zone starves, and the pump chugs. Second, economics: pipe bigger than the calculation costs money for no hydraulic gain. The design finds the diameter where the friction loss over the run stays inside the budget the hydraulic calculation allows — typically the mainline is sized so that, with the zones as designed, the pressure at the farthest zone end still lands in the working range of the emitters.

In practical terms: a one-acre system might run a 63–90mm mainline; a five-acre farm a 90–110mm; a ten-acre commercial farm a 110mm+ with the routing engineered. Those figures are the shape of the answer — your farm's real number comes from its real flow and real distances, which is exactly what the design calculates.

Pressure rating

Pipe is sold at a pressure rating (commonly 6 or 10 bar for HDPE). The rating must cover the working pressure plus a margin — the working pressure is what the pump or tank actually delivers, which the design knows. A pipe rated below the real pressure doesn't fail in a dramatic way; it fatigues, at a joint, in the dry season.

Routing — the second half of "pipe"

• The mainline route sets the whole farm's pressure behaviour: a direct route through difficult ground can cost more than a slightly longer easy one — terrain is part of the hydraulic picture.
• Zone take-offs come off the mainline at each block, valved and labelled — the labels matter the first time a leak is traced in the rain.
• Future blocks: the mainline route is drawn for the farm's intended full extent, even where phase one only uses part of it — extending a mainline later is a dig-and-fuse job you'd rather do once.

Common mistakes

• Undersizing the mainline to save the pipe line on the quote — the field pays for it in pressure for the life of the system.
• Wrong joints. A compression fitting is fine; a crimped, taped or "we'll see how it goes" joint is a leak waiting for the first full-pressure run. The fittings page covers it.
• Piping over stones and roots without bedding — punctures and slow leaks, both showing up as "the system lost pressure".
• Ignoring elevation. Pipe that climbs 20 m to a ridge carries the field at the bottom of a pressure loss — the design accounts for it; a guess doesn't.

Choosing pipes

Material (HDPE for mains), diameter (from the flow/distance calculation), rating (above working pressure), and route (terrain, extension, access). All four are in the design document, priced per metre. For your farm's specification: request a quote.