LND/Hard Landscaping/TBT-LND-013

Irrigation System Installation

Landscaping & External Works › Hard Landscaping › Irrigation System Installation

Presenter		Project
Location		Date

Irrigation system installation involves trenching, pipe laying, valve fitting, and connection to water supplies.
Trenches for irrigation pipes are typically 300–600mm deep but still present buried service risks.
Pipe materials include MDPE, PVC, and polypropylene that require cutting and solvent welding or push-fit jointing.
Solvent cement for PVC joints releases volatile fumes requiring COSHH controls in enclosed areas.
Pop-up sprinkler heads and valve boxes are installed flush with finished ground levels.
Connection to mains water supplies may require backflow prevention devices to protect potable water quality.
Electrical connections for controllers and solenoid valves must be made by qualified electricians.
Pressure testing of the installed pipework confirms joints are watertight before backfilling.
Irrigation work often takes place alongside other landscaping activities, requiring trade coordination.
Trenching near mature trees requires careful routing to avoid root damage and tree protection zones.

Buried services	Even shallow irrigation trenches can encounter gas, electricity, water, and telecoms services below ground.
Chemical exposure	Solvent cements for PVC pipe joints release harmful vapours that require ventilation and PPE.
Water quality	Incorrect connection without backflow prevention can contaminate the public drinking water supply.

Don't

Locate buried services using CAT and Genny before trenching for irrigation pipes
Use RPE and adequate ventilation when using solvent cement for PVC pipe joints
Install backflow prevention devices where connecting to mains water supplies
Pressure test the completed pipework before backfilling trenches
Route trenches clear of tree root protection zones to avoid root damage
Ensure electrical connections for controllers are made by a qualified electrician
Coordinate irrigation installation with other landscaping trades on site
Check pipe materials and fittings are compatible with the water pressure and quality
Wear knee pads when working at ground level during valve box and head installation
Record the as-built irrigation layout including pipe routes and valve locations

DON'T trench for irrigation pipes without checking for buried services first
DON'T use solvent cement in unventilated trenches or enclosed spaces without RPE
DON'T connect irrigation to mains water without a backflow prevention device
DON'T backfill over pipework before completing the pressure test successfully
DON'T route trenches through tree root protection zones without arborist approval
DON'T make electrical connections to controllers without qualified electrician involvement
DON'T leave open trenches unguarded when other trades or the public are nearby
DON'T use incompatible pipe materials or fittings not rated for the system pressure
DON'T skip the as-built record — buried irrigation is difficult to locate later
DON'T kneel directly on hard ground during prolonged installation without knee protection

See also: Landscaping Safety Awareness | Below Ground Drainage Installation

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