Maximum roof area per downpipe
One downpipe should service no more than 15 square metres of roof area.
Learn how to contain and direct water effectively within your property boundaries.
Definition
Stormwater runoff is:
- Rainwater collected from roofs, paved areas and driveways; and/or
- Water discharged from overflowing or emptied swimming pools.
Responsibilities for property owners
Property owners are legally responsible for containing stormwater runoff within their property boundaries under common law and the Local Government Act 1995. Runoff must not flow onto or cause damage to neighbouring properties. The most effective way to manage stormwater is through catchment systems such as soakwells, spoon drains or similar methods that collect and disperse water from gutters and downpipes.
Designing an effective drainage system
Stormwater systems must be installed in accordance with the following requirements:
Maximum distance between downpipes
The distance between downpipes should not exceed 12m, in line with the National Construction Code.
Overflow water management
Overflow water should be directed away from buildings to prevent ponding or damage to footings and boundaries.
Clearances for soakwells
As a general guide:
- The minimum setback for a soakwell should be at least the same as its width, provided the width is equal to or greater than the depth of the soakwell. This clearance helps prevent undermining of footings, fencing or retaining walls on or near property boundaries.
- Soakwells should not be installed in narrow spaces where there is insufficient drainage area for water to soak into the ground.
The following table provides a general guide to common concrete soakwell sizes and the approximate roof or paved surface area they can drain under normal rainfall conditions.
| Internal diameter (mm) | Length (mm) | Capacity (litres) | Approx. surface area drained (m²) |
|---|---|---|---|
| 600 | 600 | 180 | 14 |
| 900 | 600 | 385 | 31 |
| 900 | 900 | 580 | 47 |
| 1200 | 1200 | 1300 | 111 |
| 1800 | 600 | 1550 | 125 |
| 1800 | 1200 | 3100 | 250 |
Note: These figures are general recommendations based on typical rainfall. Actual performance may vary depending on soil type (e.g. clay, sand or limestone) and site conditions.
Disclaimer: This information is provided in good faith to assist residents. The City accepts no responsibility for any loss or damage arising from its use.
