Learn about the requirements and responsibilities for installing soakwells.
Definitions
- Soakwells: A soakwell is an underground tank which allows water to seep away without causing damage to surrounding areas.
- Stormwater runoff: Rainwater that is collected from roof and paved areas on an around the dwelling on the property.
- Water runoff: Swimming pool water discharged from overflowing or emptied swimming pools.
Property owner obligations
Property owners have a statutory obligation under common law and the Local Government Act 1995 to confine water runoff within their property boundaries.
The most effective way to achieve this objective is to provide catchment areas such as soakwells, spoon drains or similar methods to disperse the rainwater collected from gutters and downpipes from roof and paved areas.
Important note: One downpipe is required for approximately 15 square metres of roof area. The distance between downpipes should not exceed 12 metres in accordance with the Building Code of Australia.
It is necessary to design and install a system so that when overflowing occurs any water is directed away in a manner which ensures it does not pond against, or enter into, the building or adjacent properties.
Clearances for soakwells away from buildings and boundaries
As a general guide the setbacks for soakwells should be a minimum of the width of the soakwell away from buildings and boundaries, providing that the width is greater or equal to the depth of the soakwell.
The purpose of this procedure is so that when the soakwells are being placed in the ground, the excavation does not cause undermining of fencing and retaining walls or other adjacent buildings on boundaries or footings to buildings within the property.
It is not recommended to install soakwells where there are narrow clearances between buildings and boundaries, as there would not be sufficient drainage area for water to be drained into the soil.
Please find below a table indicating some common sizes of concrete soakwells for rainwater dispersion. The soakwell sizes required for the area of roof or paved areas are also provided as a guide.
Capacity
1. Internal diameter (mm) | 600 | 900 | 900 | 1200 | 1800 | 1800 |
| 2. Length (mm) | 600 | 600 | 900 | 1200 | 600 | 1200 |
| 3. Weight (kg) | 185 | 350 | 540 | 1100 | 900 | 1800 |
| 4. Capacity (ltrs) | 180 | 385 | 580 | 1300 | 1550 | 3100 |
| 5. Approx surface area drained | 14 | 31 | 47 | 111 | 125 |
Important note: the calculations provided above are recommended based on normal rainfall conditions. Excessive stormwater conditions can cause overflow depending on the soil type e.g.clay, limestone, etc.
More information and contact
For more information about residential stormwater runoff requirements, please contact the City's Building Services on 9400 4000 or info@joondalup.wa.gov.au.