Checking that your downpipes are correctly connected to the stormwater system is one of the most important — and most overlooked — parts of home maintenance in New Zealand. A misconnected or blocked downpipe can send water pooling against your foundations, flooding your subfloor, or even illegally discharging into the wastewater (sewage) system. The good news is that a basic inspection is something most homeowners can do themselves.
Why Correct Downpipe Connection Matters
Under the NZ Building Code (specifically Clause E1 – Surface Water), stormwater from your roof must be managed so it doesn't cause damage to your property or neighbouring land. Downpipes are the link between your gutters and the stormwater drainage network, and if that link is broken, blocked, or wrongly connected, you can end up with:
- Flooding around foundations and in subfloor spaces
- Erosion of garden beds and driveways
- Moisture ingress into walls and framing
- Illegal discharge into the wastewater system (which can attract council fines)
For more on how the Building Code applies to surface water, visit MBIE Building Performance.
What You'll Need
- A garden hose with good pressure
- A torch
- A screwdriver or probe (for checking joints)
- Safety glasses
- A stable ladder (if inspecting at height — always follow safe ladder practice)
Before climbing any ladder, review safe working-at-height guidance from WorkSafe NZ.
Step 1 — Trace the Downpipe from Top to Bottom
Start at the gutter outlet where the downpipe begins and follow it visually all the way down to where it enters the ground or connects to a surface drain. Look for:
- Loose or missing brackets allowing the pipe to pull away from the wall
- Cracked, split, or corroded pipe sections (common in older PVC or cast iron pipes)
- Joints that have separated or are leaking — look for staining or moss growth as a clue
- Any section that has been redirected or capped off without a proper connection
Check the Shoe (Bottom Bend)
The shoe is the curved fitting at the base of the downpipe. It should direct water into a drain inlet, a soakage pit, or a kerb outlet — not just onto the ground or against the house wall.
Step 2 — Run Water and Watch
This is the most reliable DIY test. Put your hose into the top of the downpipe (or into the gutter above it) and run a good flow of water for 60–90 seconds. Then:
- Watch the base of the downpipe — water should flow away freely into the drain, not back up or overflow.
- Check around the foundation — no water should be pooling against the house.
- Look for leaks along the pipe — wet patches on the wall or ground mid-run suggest a cracked joint.
- Check the drain inlet — if water backs up quickly, the underground drain may be blocked or undersized.
Step 3 — Confirm It's Going to Stormwater, Not Wastewater
This is critical. In New Zealand, stormwater and wastewater are separate systems in most urban areas. Connecting a downpipe to the wastewater (sewage) drain is illegal and can cause sewage overflows during heavy rain.
If your home was built before the 1980s, or has had DIY plumbing work done, there's a real chance a downpipe may have been incorrectly connected. Signs to look for:
- The downpipe connects to a gully trap (the small open drain near your laundry or bathroom) — this is wrong
- The underground pipe runs toward the house rather than toward the street or a soakage area
- Your council's stormwater map (available from most council websites) shows no stormwater connection near your property
If you're unsure, contact your local council's drainage team — they can often tell you where your legal stormwater connection point is.
Step 4 — Inspect Soakage Pits and Surface Drains
Some NZ properties, particularly in rural areas or on large sections, use soakage pits instead of a piped stormwater connection. Check that:
- The soakage area isn't saturated or overflowing after rain
- The pit hasn't collapsed or become blocked with silt
- Water isn't tracking toward the house or a neighbouring boundary
BRANZ has useful technical guidance on stormwater management and drainage around buildings.
Common Problems and Quick Fixes
| Problem | Likely Cause | DIY Fix? |
|---|---|---|
| Water overflowing at base | Blocked underground drain | Flush with hose; call a drainlayer if blocked |
| Leaking joint mid-pipe | Cracked fitting or loose collar | Replace fitting (DIY if above ground) |
| Downpipe discharging onto ground | Missing drain connection | Requires proper drain connection — call a drainlayer |
| Water pooling at foundation | Blocked or missing shoe | Clear blockage; reposition shoe |
| Pipe connected to gully trap | Incorrect connection | Must be corrected by a licensed drainlayer |
When to Call a Professional
Above-ground downpipe repairs — replacing a cracked section, refitting a bracket, or clearing a blockage — are generally fine for a competent DIYer. However, any work on underground drainage is restricted work under the Plumbers, Gasfitters, and Drainlayers Act 2006. This means connecting, disconnecting, or altering underground stormwater or wastewater pipes must be carried out by a licensed drainlayer.
Check that your tradesperson is registered with the Plumbers Gasfitters & Drainlayers Board. You can also find qualified local gutter cleaners and drainage specialists on tradedirectory.co.nz.
If you suspect your downpipe is connected to the wastewater system, don't delay — contact a licensed drainlayer and your local council promptly.
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