Knowing whether your downpipe connects to the stormwater system or a soakage pit is more important than many homeowners realise — it affects how well your property drains, whether you're complying with your council's rules, and how you should maintain your gutters and downpipes. In most cases you can do a bit of detective work yourself, but some situations will need a licensed drainlayer to confirm.
Why It Matters
In New Zealand, roof rainwater must be directed away from your home's foundations in a controlled way. Depending on your section's soil type, slope, and your local council's requirements, this is done either by connecting to the public stormwater network (via a pipe under the ground) or by discharging into a soakage system — typically a pit, trench, or rubble drain that lets water slowly percolate into the soil. Getting this wrong can lead to flooding, foundation damage, or even a compliance issue with your local council.
Step 1 — Check Your Property File or LIM Report
The quickest starting point is your Land Information Memorandum (LIM) or property file, available from your local council. These documents often include drainage plans showing whether your site was designed with stormwater connection or soakage. If you don't have these, contact your council's building or drainage department — many councils now offer online property file requests.
Step 2 — Look at Where the Downpipe Goes Underground
Trace your downpipe from the gutter down to where it enters the ground. Then look for these clues:
- Stormwater connection: The downpipe typically connects to a PVC or earthenware pipe that runs toward the street, a kerb outlet, or a council drain. You may see a small grated stormwater pit (also called a sump) nearby at ground level.
- Soakage system: The pipe may terminate at a rubble-filled pit, a perforated pipe in a gravel trench, or simply disappear into the ground with no visible hard connection. There's often no pit lid or grate — just a covered area of ground, sometimes slightly sunken or greener than surrounding lawn.
- Discharge to ground or garden: Some older homes simply let the downpipe discharge onto a concrete splash pad or into a garden. This is generally not compliant with modern NZ Building Code requirements under Clause E1 (Surface Water).
Step 3 — The Water Test
A simple field test: on a dry day, run a garden hose into the top of the downpipe (or ask someone to pour a bucket of water in at the gutter). Then watch carefully:
- If water appears at a kerb outlet, street drain, or stormwater pit within a minute or two, you're likely connected to stormwater.
- If the water simply disappears into the ground with no visible outlet, you probably have a soakage system.
- If water backs up, pools, or takes a very long time to drain, your soakage pit may be blocked or failing — a common issue in clay-heavy NZ soils.
Step 4 — Check the Soil and Site Conditions
Soakage systems only work well in free-draining soils like sandy loam or pumice. If your property has heavy clay soil (common in Auckland, Hamilton, and parts of Wellington), a soakage system may have been installed but could be underperforming. Properties on steep sites or with high water tables are also less suited to soakage.
If you're unsure about your soil type, BRANZ has guidance on drainage and site assessment for NZ conditions.
Step 5 — Look for a Stormwater Pit or Inspection Chamber
Many properties have a small square or round lid set into the ground near the house or driveway — this is often a stormwater inspection chamber. If you can safely lift the lid (use gloves), look inside: a pipe running toward the street strongly suggests a stormwater connection. Never enter or reach into any underground chamber.
Common Setups by Era and Region
| Era | Common System |
|---|---|
| Pre-1970s homes | Soakage pits or open discharge common |
| 1970s–1990s | Mix of soakage and stormwater connection |
| Post-2000 new builds | Usually connected to council stormwater |
| Rural/lifestyle blocks | Soakage or discharge to land typical |
Note that requirements vary significantly by council — always check with your local authority.
What If I Have Both?
Some properties have a split system — for example, front downpipes to stormwater and rear downpipes to soakage. This is not unusual, especially on larger sections or where the stormwater main doesn't reach the back of the property.
Keeping Your System Working
Regardless of which system you have, blocked or overflowing gutters are the enemy. Leaves, debris, and sediment can overwhelm both stormwater connections and soakage pits. Regular gutter cleaning — at least once a year, or twice if you have overhanging trees — is the best preventive maintenance you can do. You can find qualified local gutter cleaners on tradedirectory.co.nz.
For soakage systems specifically, avoid planting trees or large shrubs nearby, as roots can block or collapse the pit. Also avoid parking heavy vehicles over a soakage area.
When to Call a Professional
Drainage work is restricted work in New Zealand. Any modifications, repairs, or new connections to your stormwater or soakage system must be carried out by a licensed drainlayer registered with the Plumbers, Gasfitters and Drainlayers Board (PGDB). This includes connecting a new downpipe to the stormwater main or installing a new soakage pit.
Call a professional if:
- You can't determine where your downpipe drains after following these steps
- Water is pooling near your foundations after rain
- Your soakage system appears to be failing or backing up
- You want to add or relocate a downpipe
- You're buying or selling a property and need drainage confirmed
A licensed drainlayer can use a CCTV drain camera to trace your pipes definitively. You may also need a building consent for new drainage work — check with your council, as some minor work may be exempt under Schedule 1 of the Building Act, but this must be confirmed before you start. See MBIE Building Performance for guidance on consents.
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