How to bury irrigation pipes: depth and techniques
Practical guide to burying irrigation pipes: correct depth, which pipe to use, how to open trenches in established lawn and how to protect crossings under paths.
Minimum and maximum depth
Minimum burial depth: 20 cm. Below this threshold, mowers can dislodge fittings and grass roots invade joints. In frost-prone areas take main lines to 30–35 cm.
Maximum practical depth: 40–45 cm. Beyond that, excavation becomes laborious with no meaningful benefit. Exception: pipes crossing vehicle traffic areas — go to 50–60 cm with a protective sleeve.
Opening trenches in established lawn
The cleanest method is a narrow cut with an electric edger: open a 5–6 cm slot, just wide enough for the pipe. The lawn closes back with almost no visible trace within 2–3 weeks.
For wider trenches, keep the removed turf sod and replace it over the filled trench. With regular watering it recovers in 10–15 days. For gardens over 300 sq m consider renting a trenching machine.
Which pipe to use underground
Use high-density polyethylene (HDPE), PN 6 or PN 10. Main line: 25 mm. Branch lines: 20 mm. HDPE is flexible, frost-resistant, does not corrode and lasts over 30 years buried.
Avoid rigid grey PVC: it cracks with frost. Avoid low-density PE agricultural pipe: it deforms under sustained pressure.
Crossings under paths and paved areas
Don't excavate under a path — push through. Sharpen a 20 mm steel rod and drive it through with a mallet, then feed the HDPE pipe behind it.
Leave the sleeve pipe slightly longer on both sides: if you need to add a line in future, just thread the new pipe through without demolishing anything.
Map the system before backfilling
Before covering trenches, photograph everything: overhead shots every 3–5 m documenting pipe routing and every fitting location. Store with the date. In five years you will know exactly where to dig without risking an existing line.
Better still: note distances from walls or boundaries on a rough sketch. A phone photo of the sketch is enough. Fifteen minutes now saves hours of exploratory digging later.