Irrigation almost never goes into bare dirt. It goes into a lawn the homeowner already likes, which makes this job different from every other kind of trenching: the finished result is judged on what you can't see.
That's why the trench-or-plow decision matters so much here, and why it's the first thing to settle.
Trench or Plow?
Vibratory plow — a vibrating blade slices through the soil pulling pipe or wire behind it. Leaves a narrow slit that closes and heals in a few weeks. Minimal disturbance, minimal cleanup, and the customer can't find the line by August.
The limits are real: plows need soil that accepts the blade. Hard dry clay, stony ground, and heavy root zones don't cooperate. Pipe diameter is limited, and depth control is less precise than a trencher.
Trencher — cuts an open trench at set depth, spoil to one side. Handles larger pipe, harder soil, and exact depth requirements. Costs you an open trench to backfill and turf to restore.
Most irrigation contractors own both. Plow the laterals across open turf, trench the mainline and anywhere the plow won't go.
Before You Start
Call 811. Every job, with lead time. Irrigation runs cross the entire yard, which means crossing every service lateral on the property. This is the highest-strike-risk work in landscaping.
Locate private utilities too. 811 marks public utilities to the meter. It does not mark the line from the meter to the house, the gas line to the grill, the electric to the shed, or the septic. Those are the owner's responsibility and they're exactly what you'll hit.
Confirm depth requirements. Frost depth governs mainline burial in cold climates. Check local code — it varies significantly.
Plan the layout first. Head placement, zone design, and valve locations determine where the pipe goes. Don't start cutting until the design is set.
Check backflow requirements. Most jurisdictions require a backflow prevention device on irrigation systems, and many require it be installed and inspected by a licensed installer.
Steps
1. Mark the layout. Paint the runs, head locations, and valve box positions.
2. Cut sod where you're trenching and set it aside on a tarp. Replacing the original sod over the trench heals far faster than seeding, and it's the difference between an invisible repair and a visible strip.
3. Plow or trench the runs.
Plowing: pull the pipe with the blade, maintaining steady speed. Watch for the blade riding up in hard ground.
Trenching: advance at a consistent pace. Let the chain cut rather than pushing. Keep the spoil on one side for easier backfill.
4. Install pipe and fittings. Check for debris in the pipe before gluing or clamping, and support the pipe on undisturbed bottom rather than loose spoil.
5. Pressure test before backfilling. Every time. Finding a leak after the trench is closed and the sod is back is a bad afternoon.
6. Backfill in lifts and compact lightly. Loose backfill settles and leaves a visible depression along every run — that's the most common complaint on irrigation jobs.
7. Replace sod or seed. Water it in. Sod laid back over a properly compacted trench disappears in a couple of weeks.
Trench Safety
Irrigation trenches are usually shallow, but if you're going deeper for a mainline or a valve pit, know this: OSHA requires a protective system for excavations 5 feet deep or greater, and soil can collapse without warning at depths people assume are safe. Never enter an unprotected trench at that depth. Trench collapse kills people every year, and it's entirely preventable.
Common Mistakes
Skipping 811, or assuming it covers private lines. The most costly error available.
Not pressure testing before backfill. Always test first.
Loose backfill. Settlement leaves a visible line across the lawn for a year.
Discarding the sod. Original sod replaced over the trench heals dramatically faster than seed.
Plowing in unsuitable soil. Forcing a plow through hard clay or rock does poor work and beats up the machine. Switch to trenching.
Wrong depth. Under frost depth means freeze damage. Check local code.
Which Yellow Jacket Model
YJ1000 — the irrigation contractor's machine. Narrow, tracked, 25 hp Kubota diesel.
YJ1200 — for drainage-heavy work and larger installations.
Both trenchers and plows are sustained hydraulic loads — flow capacity matters more than lift capacity for this job.
FAQ
How deep should irrigation lines be?
Mainline depth is typically governed by frost depth; laterals are usually shallower. Requirements vary considerably by region — check local code rather than a general rule.
Plow or trench for laterals?
Plow where soil allows — the turf recovery is dramatically better. Trench where the ground won't take a plow or where you need precise depth.
How much turf damage should I expect?
Plowing: a slit that closes in weeks. Trenching: a visible line that needs proper backfill, compaction, and sod or seed. The machine itself, on tracks, leaves minimal marking.
Will it work in clay?
Trenching, yes. Plowing in hard dry clay, poorly — moisture helps significantly.
What about tree roots?
A trencher cuts through roots, and large roots slow it considerably. Also consider the tree: cutting major roots has consequences. Route around significant trees where you can.
Do I need a licensed installer?
Many jurisdictions require licensing for irrigation work, particularly anything involving potable water connection and backflow prevention. Check before you install.