Blocked downpipes are one of the most common causes of water damage in New Zealand homes — and on a two-storey house, clearing them safely takes a bit more planning than a single-storey job. The good news is that with the right tools and a careful approach, many blockages can be cleared as a DIY task. However, working at height always carries real risk, so know your limits before you climb.
Why Downpipes Block Up
NZ's varied climate — from leafy Auckland suburbs to windy Wellington — means gutters and downpipes collect all sorts of debris. Common culprits include:
- Leaves and twigs from overhanging trees
- Moss and lichen washed down from the roof
- Sediment and dirt that compacts over time
- Bird nests or feathers lodged in the pipe
- Damaged or misaligned pipe sections that catch debris
A blocked downpipe can cause gutters to overflow, leading to water ingress, rotting fascia boards, foundation dampness, and even interior leaks — all issues that can affect your home's compliance with the NZ Building Code.
Tools and Materials You'll Need
- A sturdy, rated extension ladder (minimum 1.2 m past the gutter line)
- Ladder standoffs or stabilisers
- Heavy-duty rubber gloves and safety glasses
- A garden hose with a strong nozzle or a pressure washer (low setting)
- A plumber's drain snake (hand auger) — available from Bunnings or Mitre 10
- A bucket and tarpaulin to catch debris
- A helper to foot the ladder
Safety First — Working at Height
Working on a two-storey house means you could be 5–7 metres off the ground. Falls from ladders are a leading cause of serious injury in NZ. WorkSafe NZ recommends:
- Never work alone — always have someone footing the ladder
- Use a ladder rated for your weight plus tools
- Set the ladder at a 75-degree angle (1 out for every 4 up)
- Wear non-slip footwear
- Don't overreach — move the ladder instead
- Avoid working in wet or windy conditions
If you're not confident working at this height, stop here and call a professional roofer.
Step-by-Step: How to Clear a Blocked Downpipe
Step 1 — Locate the Blockage
Before climbing, run a hose into the top of the downpipe from ground level if possible. If water backs up immediately, the blockage is near the top. If it drains slowly, it may be lower down or at the shoe (the curved outlet at the bottom).
Step 2 — Clear the Gutter First
A blocked downpipe is often caused by a full gutter. Scoop out debris from the gutter around the downpipe outlet before tackling the pipe itself. Place debris in your bucket — don't let it wash into the downpipe.
Step 3 — Flush From the Top
With your helper footing the ladder, carefully insert the hose into the top of the downpipe and turn it on full. The water pressure often dislodges soft blockages. Stand to the side — debris can shoot out the bottom.
Step 4 — Use a Drain Snake
If flushing doesn't work, feed a hand auger (drain snake) down from the top of the pipe. Rotate it as you push to break up compacted debris. Withdraw slowly and clear the auger head. Repeat until the pipe runs freely.
Step 5 — Check the Shoe and Drain
Once the pipe is clear, check the bottom outlet (shoe) and any underground drain connection. Debris often collects here. Clear by hand or with the hose.
Step 6 — Final Flush and Inspection
Flush the entire system with the hose from the top. Water should flow freely out the bottom. While you're up there, check for:
- Cracked or separated pipe joints
- Loose brackets or clips
- Rust or corrosion on metal downpipes
- Gutter sag or misalignment
Preventing Future Blockages
- Install gutter guards — mesh or foam inserts reduce leaf build-up
- Trim overhanging trees where safe to do so
- Clean gutters and downpipes at least twice a year — autumn and spring are ideal in most NZ regions
- Consider downpipe strainers (leaf catchers) at the gutter outlet
Regular maintenance also helps keep your home compliant with moisture management requirements under the Building Code, particularly clauses E1 (surface water) and E2 (external moisture).
When to Call a Professional
Call a qualified roofer or drainage specialist if:
- You're not comfortable working at height on a two-storey house
- The blockage won't clear with flushing or a drain snake
- You notice cracked, separated, or corroded downpipe sections that need replacing
- Water is tracking behind the cladding or into the wall cavity
- The underground drain connection appears blocked (this may involve drainlaying, which is restricted work under the Plumbers, Gasfitters and Drainlayers Board — it must be carried out by a licensed tradesperson)
- Your roof or guttering needs structural repairs that may require a building consent — always check with your local council
A licensed roofer can also advise whether your downpipe system is adequately sized for your roof catchment area — undersized pipes are a common issue in older NZ homes. You can find experienced local roofers on tradedirectory.co.nz.