Main Line (HDPE)

The irrigation main line carries the combined flow before it splits into submains or zones. This diagram shelf currently lists a PE mainline pipe; an irrigation mainline pipe must be selected for the actual simultaneous flow, pressure loss and installation method.

Confirm outside diameter, pressure class, length and joining system on the product. Include valves, filters and elevation changes in the hydraulic plan. Smaller lateral tubing should not be substituted for a high-flow main simply because its connection can be adapted.

Where and when to use it

An irrigation main line carries water from the pump or source-control station toward zone branches. The route currently has a very limited product selection, so use it to understand function and verify the actual item offered. A farm mainline should be planned from the peak simultaneous zone flow, route length, elevation and future service access, not from the diameter of one drip lateral.

How it works

The mainline transports combined flow under pressure. Friction and fittings consume head before water reaches a submain, valve or emitter. Larger pipe may reduce friction but has different installation cost and support needs; selecting diameter is a hydraulic and economic decision. Its joints, isolation points and air management affect system reliability.

How to plan and install it

1. Locate source, treatment station and zone takeoffs on a site plan.
2. Calculate maximum simultaneous flow and acceptable pressure loss to the farthest branch.
3. Choose rated pipe, compatible fittings, isolation and air-release points where the design requires them.
4. Flush and pressure-test the line before attaching small emitters or burying joints.

Operation and maintenance

Maintain an as-built mainline map and keep valve boxes accessible. Check for leaks, pressure surges and unexpected flow changes. A downstream dry zone may originate from a mainline restriction or closed valve; confirm pressure along the route before replacing field hardware.

Common questions

How to connect irrigation to main water line?

Identify whether the source is potable, reclaimed or private and obtain the required approved isolation or backflow protection. Size the takeoff, valve, filter and mainline for peak zone flow; use compatible pipe and fittings, then test the connection and measure pressure while watering.

Is a mainline the same as drip tubing?

No. Mainlines carry combined supply; drip tubing normally serves individual crop rows or outlet groups.

Technical reference: USDA NRCS, National Engineering Handbook: Microirrigation. Use the selected product manual and local requirements for final design.