Understanding stormwater and subsoil drainage for Sydney homes.
Stormwater and sewer are completely separate systems.
Stormwater takes rainwater directly to waterways without treatment.
Common problems: blocked downpipe connections, broken or collapsed pipes, inadequate drainage, surface water pooling, subsoil drain failure, damaged boundary traps, and boundary trap vent blockages.
What is subsoil drainage? Subsoil drains (also called agricultural drains or ag drains) are installed below ground level to collect and redirect groundwater away from your property's foundations.
Subsoil drainage is essential in Sydney's clay-heavy soils which retain moisture and cause hydrostatic pressure against foundations.
Signs you need subsoil drainage include rising damp, water seepage through basement walls, waterlogged gardens, and efflorescence on brick walls.
What is a boundary trap? A boundary trap is the connection point between your property's sewer system and Sydney Water's main sewer line.
Boundary trap replacement is required when the trap is cracked, root-invaded, or collapsed.
Boundary trap vents allow air into the sewer system to prevent vacuum locks.
Common issues include boundary trap overflow, blocked boundary trap vents, and root intrusion.
Solutions: pit and pipe drainage $1,500-$5,000, subsoil drainage installation $100-$200 per metre, channel drains $100-$200 per metre, French drains $80-$150 per metre, boundary trap replacement $800-$2,500, rainwater tanks.
Council regulations cover discharge requirements and on-site detention..