GAP Trade Services Pty Ltd — Drainage in Killara

Subsoil (ag pipe) drainage installation costs $30–$80 per linear metre. Stormwater drainage systems cost $3,000–$15,000 depending on scope. A French drain for a typical yard costs $2,000–$6,000. Blocked drain clearing by a plumber costs $150–$500. Get multiple quotes as drainage projects vary greatly in scope and complexity.

Standing water after rain that takes more than 24–48 hours to drain, soggy patches that never fully dry, water pooling near the house foundation, damp or water-stained interior walls, cracked or heaving concrete paths, and unexplained lawn die-off in patches are all signs of drainage problems requiring professional assessment.

Surface drainage removes water visible on top of the ground using graded surfaces, channels, and grates. Subsoil drainage (ag pipe wrapped in geofabric, installed 300–600mm deep) collects water that has already entered the soil and redirects it to a drainage point. Most drainage problems require both surface and subsoil solutions working together.

A French drain is a gravel-filled trench with a perforated pipe that collects groundwater and channels it away from the problem area. The trench is lined with geofabric to prevent soil entering the pipe. They're very effective for soggy lawns, foundation moisture, and retaining wall drainage. They typically discharge to an absorption trench, pit, or street stormwater.

Stormwater drainage that connects to the public stormwater system (kerb, pit, or mains) must be done by a licensed plumber in all states. Subsoil drainage (ag pipe) that discharges to an absorption trench or existing drainage pit may not require a plumber. Internal sanitary drainage always requires a licensed plumber. Check with your local council.