How to Check If Your Home's Downpipes Are Blocked or Damaged

Blocked or damaged downpipes are one of the most common causes of water damage in New Zealand homes. Catching a problem early can save you thousands in repairs — and the good news is that a basic inspection is something most homeowners can do themselves with a little care and the right approach.

Why Downpipes Matter

Downpipes carry rainwater from your gutters down to the stormwater drainage system. When they're blocked or cracked, water can overflow against your cladding, pool around your foundations, or seep into your walls — all of which can lead to moisture damage, rot, and mould. Under the NZ Building Code, your home's drainage system (covered under Clause E1 – Surface Water) must effectively manage stormwater, so keeping downpipes in good working order isn't just good practice, it's part of maintaining a compliant home.

If you're a landlord, note that the Healthy Homes Standards include requirements relating to moisture ingress and drainage in rental properties. Check the Tenancy Services website for the specific requirements that apply to your property.

Tools You'll Need

Before you start, gather the following:

• A sturdy ladder (rated for your weight, with non-slip feet)
• Garden hose with good water pressure
• A torch
• Stiff wire or a plumber's drain snake (optional)
• Safety glasses and gloves
• A helper to steady the ladder

Safety first: Always follow safe ladder practices. Set your ladder on firm, level ground and never lean out past the rails. If your roof or gutters are more than a single storey up, consider hiring a professional rather than taking the risk.

Step 1 – Visual Inspection from the Ground

Start from the ground before you climb anything. Walk around your home and look at each downpipe carefully:

• Check for visible cracks, splits, or holes in the pipe body
• Look for rust streaks or staining on the pipe or cladding below (common with older steel downpipes)
• Notice any sections that have pulled away from the wall or lost their brackets
• Look at the bottom outlet — is there debris, mud, or plant growth blocking the exit?
• After heavy rain, check whether water is overflowing from the gutters near a downpipe connection — this often signals a blockage below

Step 2 – Check the Gutters and Inlet

Once you're safely on a ladder, inspect where the gutter connects to the top of the downpipe (the inlet or shoe):

• Remove any visible leaf litter, moss, or debris from the gutter around the inlet
• Look down into the top of the downpipe with your torch — can you see daylight at the bottom? If not, there may be a blockage
• Check for sagging gutters that don't drain toward the downpipe properly

Step 3 – The Hose Test

This is the most reliable DIY method for finding a blockage:

1. Insert your garden hose into the top of the downpipe
2. Turn the water on to a moderate flow
3. Watch the bottom outlet — water should flow freely within a few seconds
4. If water backs up and overflows at the top, you have a blockage somewhere in the pipe
5. If water trickles out slowly, there may be a partial blockage or a crushed section

For a minor blockage, you can try feeding a drain snake or stiff wire down from the top to dislodge debris. Flushing again with the hose usually clears it.

Step 4 – Inspect the Underground Connection

At ground level, downpipes typically connect to an underground stormwater drain via a shoe (a curved fitting) and sometimes a trap or gully. Check:

• Is the gully or outlet clear of soil, leaves, and debris?
• Is there any standing water around the base of the downpipe after rain?
• Are there any sunken or cracked areas in the ground nearby, which could indicate a collapsed underground pipe?

Underground stormwater pipes are part of your drainlaying system. Any work on underground drainage is restricted work under the Plumbers, Gasfitters and Drainlayers Board (PGDB) regulations and must be carried out by a licensed drainlayer. Don't attempt to dig up or repair underground pipes yourself.

Common Downpipe Materials in NZ Homes

If your home has older steel or cast iron downpipes, pay extra attention to rust and joint integrity. BRANZ has useful guidance on weathertightness and cladding maintenance for NZ homes.

Simple Repairs vs. When to Leave It

Homeowners can generally handle:

• Clearing debris blockages with a hose or drain snake
• Reattaching a loose bracket with appropriate screws
• Replacing a short section of uPVC downpipe with push-fit fittings (available at Bunnings or Mitre 10)
• Sealing a small crack with an appropriate waterproof sealant (such as a product from Sika)

Always check that any replacement pipe matches the existing diameter and material.

When to Call a Professional

Call a licensed building inspector or qualified tradesperson if you find:

• Significant cracking, crushing, or deformation of the downpipe
• Evidence of water damage to cladding, framing, or foundations
• Suspected underground drainage issues (this is restricted drainlaying work — contact a licensed drainlayer registered with the PGDB)
• Blockages you cannot clear after two or three attempts
• Any situation where safe ladder access is not possible

A building inspector can assess whether downpipe issues have led to broader weathertightness or structural problems. You can find qualified local building inspectors and tradespeople on tradedirectory.co.nz.

Sources & Further Reading

• MBIE Building Performance – NZ Building Code Clause E1 (Surface Water)
• BRANZ – Weathertightness and Maintenance Guidance
• Tenancy Services – Healthy Homes Standards
• WorkSafe NZ – Ladder Safety
• Plumbers, Gasfitters and Drainlayers Board – Licensed Drainlayers
• Sika NZ – Sealants and Waterproofing Products