OSD’s and stormwater detention tanks are crucial components of stormwater management in many private and commercial properties. As such, it’s important to understand the purpose of stormwater detention systems, the installation of detention systems (OSD), alternative types of stormwater detention, and the maintenance of water detention tanks.

Purpose of stormwater detention systems

  • Stormwater detention systems delay the release of stormwater discharged from residential, industrial and commercial premises.

  • Delaying the release of stormwater can:
    • Reduce local flooding problems
    • Reduces erosion risk in urban waterways
    • Reduce the adverse effects of urban waterways on aquatic fauna

Installation of detention systems

installation of On-site stormwater detention tanks (OSD)
OSD construction

  • Stormwater storage systems are usually different from any rainwater tanks on residential properties.
  • Unlike rainwater tanks, stormwater storage systems are usually designed to drain entirely over an average span of 24 to 36 hours.
  • In general, the use of stormwater detention systems is governed by local laws enacted by councils.

Alternative types of stormwater detention

  • Stormwater detention systems take many forms including:
    • Below and above ground tanks (OSD)
    • Plastic or rubber-cell soakage pits
    • Enlarged roof-water guttering systems
    • Recessed tennis courts
    • Domestic dams and ponds

  • Using the same tank for both stormwater retention and long-term storage of rainwater is generally not considered advisable.

Maintenance of detention tanks

  • Every year stormwater detention systems on-site should be inspected to check for:
    • Sediment deposition
    • Debris blockage of screens and outlets
    • Structural damage

Maintenance of stormwater detention tanks

  • Caution; rotting organic matter inside tanks can create deadly gases that are undetectable to the human nose.

  • Never enter a confined space without adequate training, safety equipment, and another observer.


Stormwater Sydney provides complete stormwater management for commercial and residential properties. Design, Cleaning, Maintenance, Repairs, Construction, and Advisory on stormwater systems across Sydney, ensuring compliance with Sydney standards and Council regulations.

Stormwater Sydney provides design, management and consulting services across Sydney. Inspection, design, cleaning, maintenance, repairs, construction and advisory on stormwater & WSUD systems. Pits, pipes, pumps, drains, gutters, tanks and all your WSUD needs. Ensuring you comply with EPA and Councils Regulations.

Stormwater Sydney