Knowing where your drains run is one of those things you never think about — until you're planning a new deck, digging a garden bed, or dealing with a blocked or broken pipe. Fortunately, there are several practical ways to trace your drain layout, ranging from free council records to hands-on inspection methods. This guide walks you through your options, from simplest to most involved.
Start With Your Council and Property Records
Your first port of call should be your local council. Most New Zealand councils hold drainage plans (sometimes called drainage diagrams or LIM records) for properties, especially those connected to the public wastewater network. You can request these through:
- A Land Information Memorandum (LIM) from your council — this often includes drainage and stormwater details
- A Project Information Memorandum (PIM) if you're planning building work
- Direct requests to the council's infrastructure or drainage department
Some councils provide online property portals where you can view or download drainage plans for free or a small fee. Ring your council's customer service team and ask specifically for drainage as-built plans.
If your home was built or altered with a building consent, the consent documents held by council may include drainage layout drawings. These are worth tracking down before you dig anything.
Check Your Property's As-Built Plans
If you have the original as-built plans for your home (sometimes left behind by previous owners or held by your solicitor), these may show the drain layout. Look for a site plan that includes pipe runs, inspection chambers (manholes), and connection points to the street.
For newer homes, builders are required under the NZ Building Code to provide as-built documentation to the council on completion. Ask your council if these are on file.
Walk the Property and Look for Clues
A surprisingly effective method is simply walking around your property with your eyes open. Look for:
- Inspection chamber lids (round or square covers, often concrete or plastic, set into the ground)
- Vent pipes rising from the ground or through the roof — these indicate drain locations below
- Depressions or lush grass in a line across the lawn, which can indicate a leaking or shallow drain
- Downpipe outlets at the base of your house walls — these connect to either the stormwater or wastewater system
Mark each chamber you find with a stake or spray paint. Chambers are typically spaced at changes of direction, junctions, and at regular intervals along longer runs. Connecting the dots between chambers will give you a rough picture of your drain layout.
Use a Drain Rod or Tape to Measure Direction
Once you've located an inspection chamber, you can use a flexible drain rod (available from Bunnings or Mitre 10) to probe the direction a pipe runs. Feed the rod into the pipe and note which way it travels — this tells you the direction of flow and helps you map the run between chambers.
A drain tape (a long, flexible steel tape) works similarly and can give you a rough idea of the distance to the next chamber or junction.
Try a Drain Locator or Sonde
For a more accurate picture, a drain locator system uses a small electronic transmitter (called a sonde) that is pushed or flushed through the pipe. A handheld receiver above ground picks up the signal and lets you trace the pipe's path and depth without digging.
This is the same technology professional drainlayers use. You can sometimes hire locating equipment from tool hire companies, though operating it accurately takes practice. Many homeowners find it more cost-effective to simply hire a drainlayer who has the gear and knows how to use it.
CCTV Drain Inspection
If you need to know not just where your drains run but also what condition they're in, a CCTV drain camera inspection is the gold standard. A licensed drainlayer or drain inspection company feeds a camera through your pipes and records footage of the interior. This reveals:
- Exact pipe routes and depths
- Root intrusion, cracks, or collapsed sections
- Blockages or build-up
- Incorrect falls or connections
CCTV inspections are especially recommended before purchasing a property, planning an extension, or investigating a persistent blockage. The footage gives you a permanent record you can share with your council or insurer.
Stormwater vs. Wastewater — Know the Difference
New Zealand homes typically have two separate drain systems:
| System | What it carries | Where it goes |
|---|---|---|
| Wastewater (foul) | Sewage from toilets, sinks, showers | Council sewer or septic tank |
| Stormwater | Rainwater from roofs and paved areas | Council drain, stream, or soakpit |
It's important not to connect these systems — cross-connections are illegal under the NZ Building Code and can cause serious environmental harm. If you're unsure which system a pipe belongs to, a licensed drainlayer can confirm this for you.
When to Call a Professional
Some drain-finding tasks are straightforward DIY, but others require a licensed drainlayer. Under New Zealand law, drainlaying is restricted work — any new connections, alterations, or repairs to your drainage system must be carried out by (or under the supervision of) a registered drainlayer. This includes:
- Connecting new pipes to existing drains
- Relocating or replacing drain lines
- Any work on the public sewer connection
If you're planning building work near drains, or if you've found a damaged or blocked pipe, it's time to call in a professional. A qualified drainlayer can locate, inspect, and repair your drains legally and safely — and provide the documentation your council requires.
You can find licensed local drainlayers in your area on tradedirectory.co.nz.