How to Check If Your Downpipes Are Draining Properly After Cleaning

After a gutter clean, it's worth taking an extra 20–30 minutes to confirm your downpipes are actually doing their job. A blocked or slow-draining downpipe can cause water to back up into your gutters, overflow against your cladding, and eventually lead to costly moisture damage — a real concern in New Zealand's wet climate. Here's how to check everything is flowing as it should.

Why Downpipe Drainage Matters

Downpipes carry rainwater from your gutters down to either a stormwater drain or a soakage system. When they're blocked or damaged, water has nowhere to go and can pool against your foundation, saturate your soil, or seep behind cladding. Under the NZ Building Code clause E1 (Surface Water), your property's drainage must effectively remove surface and roof water — so keeping downpipes clear isn't just good practice, it's part of maintaining a compliant home. MBIE Building Performance has useful guidance on surface water requirements.

What You'll Need

• Garden hose with a good flow rate
• Torch or phone torch
• Ladder (use a stabiliser or standoff bracket for safety)
• Screwdriver (if you need to remove downpipe clips or inspection caps)
• A helper if possible

Step 1 — Do a Visual Check First

Before running any water, look at each downpipe from top to bottom:

• Check for visible dents, kinks, or crushed sections that could restrict flow
• Look for gaps or separations at the joints — these are common after years of thermal expansion
• Check the downpipe outlet at ground level isn't blocked by leaf litter, soil, or overgrown plants
• If your downpipe connects to an underground stormwater drain, make sure the grate or surround is clear

Step 2 — The Hose Flow Test

This is the most reliable DIY method:

1. Place your hose at the top of the downpipe (either via the gutter outlet or directly into the top of the pipe)
2. Turn the hose on to a strong, steady flow
3. Watch the bottom of the downpipe — water should appear within a few seconds and flow freely
4. Have your helper watch the gutter at the same time — if water backs up in the gutter rather than flowing down, there's a restriction somewhere in the pipe

What good drainage looks like: Water exits the bottom at roughly the same rate it enters the top, with no gurgling, spurting, or backing up.

Signs of a problem:

• Water trickles out slowly or not at all
• You hear a gurgling or bubbling sound inside the pipe
• Water overflows back into the gutter
• Water seeps out at a joint mid-pipe

Step 3 — Check the Underground Connection

If your downpipe connects to an underground stormwater system, run the hose for a full minute and then watch the ground nearby. Soft, soggy ground or water surfacing around the pipe base can indicate a broken underground drain or a blocked connection point. This is worth investigating further — a blocked stormwater drain can also affect neighbouring properties.

BRANZ provides research and guidance on building drainage performance that can help you understand what's normal for your home type.

Step 4 — Clear a Partial Blockage Yourself

If flow is slow but not completely blocked, you may be able to clear it yourself:

• From the top: Use a plumber's drain snake (available from Bunnings or Mitre 10) fed down from the gutter outlet
• From the bottom: Direct a strong hose jet upward into the pipe to dislodge debris
• Disassemble if needed: Many downpipes have push-fit or clip joints — you can separate sections to locate and remove a blockage manually

Always flush with the hose after clearing to confirm flow has been restored.

Step 5 — Check Soakage Pits and Rain Heads

Some NZ homes — particularly older ones — drain to a soakage pit rather than a council stormwater system. If yours does, check that the area above the pit isn't waterlogged after rain. Soakage pits can become saturated over time, especially in clay-heavy soils. If you suspect your soakage system is failing, this is a job for a drainage professional.

If your home has a rain head (a small open box where the roof drain meets the downpipe), check it's clear of debris and that water flows into the downpipe rather than overflowing the sides.

Ladder Safety — Don't Skip This

Working at height is one of the leading causes of serious injury for DIYers in New Zealand. WorkSafe NZ recommends always having a second person present when using a ladder, ensuring it's on firm, level ground, and never overreaching. Use a ladder stabiliser to keep the ladder away from the gutter itself.

When to Call a Professional

Call a qualified gutter cleaner or drainlayer if:

• The downpipe is completely blocked and you can't clear it with a hose or snake
• Water is surfacing from the ground near the downpipe base
• You suspect a broken underground drain — this may require a CCTV drain inspection
• Your downpipe is damaged, crushed, or has separated joints that need replacing
• You're not comfortable working at height

Note: Connecting or modifying underground stormwater drains is restricted drainlaying work under the Plumbers, Gasfitters and Drainlayers Act 2006 and must be carried out by a licensed drainlayer registered with the Plumbers Gasfitters & Drainlayers Board. Homeowners can maintain and clear their own above-ground downpipes, but underground drain work requires a licensed professional.

You can find experienced local gutter cleaners and drainlayers on tradedirectory.co.nz.

Sources & Further Reading

• MBIE Building Performance — Building Code clause E1 Surface Water
• BRANZ — Building Research
• WorkSafe NZ — Working at Height Safety
• Plumbers Gasfitters & Drainlayers Board — Licensed Drainlayers
• Bunnings — Drain Cleaning Tools
• Mitre 10 — Plumbing & Drainage Supplies