In most cases, yes — a homeowner can run a heat pump condensate drain pipe outside themselves in NZ. This is generally not restricted electrical or plumbing work, but there are important guidelines around where the water can discharge, how the pipe should be routed, and when you might need a professional involved.
What Is the Condensate Drain Pipe?
Your heat pump's indoor unit (the evaporator) produces condensation — water that drips off the coil as it cools or heats the air. This water collects in a drip tray and needs to drain away safely. The condensate drain pipe carries that water from the indoor unit to a suitable discharge point, usually outside.
This pipe is typically 16–20 mm diameter PVC or flexible tubing, and it runs from the indoor unit through the wall to the exterior of the house.
Is It Restricted Work in NZ?
Routing a condensate drain pipe is not classified as restricted plumbing or drainlaying work under the Plumbers, Gasfitters and Drainlayers Board (PGDB) rules, provided the water is not being connected to the household drainage system (i.e., it's discharging freely outside rather than into a waste pipe or drain).
However, if you want to connect the condensate drain into your household wastewater system — for example, into a sink trap or floor drain — that connection is restricted plumbing work and must be carried out by a licensed plumber. Always check with your local council if you're unsure about your specific situation.
The electrical connections for the heat pump itself are restricted work under the Electrical Workers Registration Board (EWRB) — only a registered electrician can connect or modify the electrical supply to the unit.
Where Can the Drain Water Discharge?
This is the most important thing to get right. Condensate water should discharge to a location that:
- Does not cause nuisance to neighbours or pedestrians (e.g., dripping onto a footpath or driveway where it could create a slip hazard)
- Does not damage the building — avoid discharging against the cladding, into a wall cavity, or near the foundation
- Does not pool near the house, which could cause moisture issues or undermine foundations
- Is ideally directed to a garden bed, lawn, or a suitable soakage area
- Complies with your local council's stormwater rules — some councils have restrictions on where surface water can discharge, so it's worth a quick call to confirm
A common and tidy solution is to run the pipe to a small gravel soakage pit or simply let it drip onto a garden area away from the house.
How to Route the Drain Pipe Outside: Step by Step
1. Plan your route
Work out the shortest practical path from the indoor unit through the wall to the outside. The pipe needs a continuous downward fall (a minimum gradient of about 1:50 is a good rule of thumb) so water flows by gravity and doesn't pool or back up.
2. Drill the wall penetration
Use a core drill or hole saw sized to suit your pipe (typically 20–25 mm). If you're drilling through a cavity wall or insulated wall, take care not to damage insulation, vapour barriers, or framing. Drill at a slight downward angle toward the outside.
3. Seal the penetration
This is critical for weathertightness. Use an appropriate exterior-grade sealant (such as a product from Sika) around the pipe where it passes through the wall. Poor sealing can allow water ingress, which is a leading cause of building damage in NZ — refer to MBIE Building Performance guidance on weathertightness if you're unsure.
4. Secure and protect the pipe
Outside, clip the pipe neatly to the wall using UV-resistant pipe clips. If the pipe will be exposed to sunlight, use UV-stabilised tubing or protect it with a conduit. Avoid leaving long unsupported runs that could sag and trap water.
5. Terminate safely
Fit a fly-screen mesh cap or similar to the end of the pipe to prevent insects nesting inside — a common issue in NZ summers.
Tools and Materials You'll Need
| Item | Where to find it |
|---|---|
| PVC or flexible condensate tubing | Bunnings or Mitre 10 |
| Hole saw / core drill bit | Bunnings or hire locally |
| UV-resistant pipe clips | PlaceMakers |
| Exterior sealant (e.g., Sika Flex) | Mitre 10 |
| Fly-screen end cap | Hardware stores |
Does This Need a Building Consent?
Routing a condensate drain pipe on its own is very unlikely to require a building consent — it falls well within Schedule 1 exemptions of the Building Act. However, if the work involves significant structural penetrations or alterations, always confirm with your local council first. The MBIE Building Performance website has useful guidance on consent exemptions.
When to Call a Professional
Consider getting a qualified tradesperson involved if:
- You want to connect the condensate drain into the household wastewater system (restricted plumbing work)
- You're unsure about weathertight sealing through your wall type (e.g., monolithic cladding, EIFS, or brick)
- The drain is backing up or not flowing — this may indicate a blockage or installation issue with the heat pump itself
- You're not confident drilling through your wall without damaging framing, wiring, or insulation
- The original heat pump installation was done by a professional and the drain wasn't completed at the time
A qualified heat pump installer or plumber can sort this quickly and ensure it's done right. You can find licensed local tradespeople on tradedirectory.co.nz.
Safety Note
Always check for electrical cables and pipes inside the wall before drilling. Use a stud finder and cable detector. Never attempt to modify the electrical connections to your heat pump — this is restricted work for a registered electrician under the EWRB.
ISO 9001
