In most cases, yes — extending the condensate drain hose on your heat pump's indoor unit is a job a capable homeowner can tackle themselves. It doesn't involve refrigerant, electrical connections, or gas, so it falls outside the legally restricted work categories in New Zealand. That said, there are a few important things to get right to avoid water damage, mould, and a unit that throws a fault code.
What Is the Condensate Drain Hose?
When your heat pump runs in cooling mode (or in heating mode in humid conditions), it pulls moisture out of the air. This moisture collects in a drip tray inside the indoor unit and drains away through a flexible hose — usually 16 mm or 19 mm diameter PVC or polyethylene tubing. If the original hose is too short to reach a suitable drain point, you may need to extend it.
Is This Restricted Work in New Zealand?
Extending a condensate drain hose is not restricted electrical, gas, plumbing, or drainlaying work under NZ law, provided you are only working on the drain hose itself and not touching any electrical wiring, refrigerant lines, or making a connection to the household drainage system that would require a licensed drainlayer.
However, if you plan to connect the extended hose directly into your home's sanitary drainage system (e.g., into a waste pipe), that connection may be considered restricted plumbing work under the Plumbers, Gasfitters and Drainlayers Act 2006. In that case, you'd need a licensed tradesperson. Check with the Plumbers Gasfitters & Drainlayers Board if you're unsure about your specific situation. Most condensate hoses simply drain to a safe outdoor location or into a laundry tub, which avoids this issue entirely.
What You'll Need
- Replacement or extension hose (match the existing diameter — typically 16 mm or 19 mm ID)
- A barbed joiner or hose coupler of the correct size
- Hose clamps (worm-drive type) or self-amalgamating tape
- A spirit level or slope gauge
- Pipe clips or saddles to secure the hose run
- Silicone sealant (optional, for any penetrations through walls)
You'll find suitable hose, joiners, and clamps at Bunnings or Mitre 10. Match the hose material and diameter to what's already fitted — check your unit's installation manual if you're unsure.
Key Rules for a Good Drain Hose Extension
1. Maintain a Continuous Fall
This is the most critical rule. The hose must slope continuously downhill from the drip tray to the discharge point — a minimum fall of around 1:50 (2 cm drop per metre of run) is a common guideline, though steeper is better. Any sag or uphill section will trap water, cause the tray to overflow, and may trigger the unit's float switch fault.
2. Keep the Run as Short and Direct as Possible
Long, convoluted hose runs are more likely to sag, kink, or block. Plan your route before you buy materials.
3. Avoid Kinks and Sharp Bends
Use gentle curves and proper clips to support the hose at regular intervals (every 500–600 mm is a reasonable guide). Kinks restrict flow and can cause backups.
4. Discharge to a Safe Location
The hose should discharge where water won't cause damage or create a slip hazard. Common options include:
- Outside, onto a garden bed or drain
- Into a laundry tub or floor waste (check if this requires a licensed plumber in your situation)
- Into a purpose-made condensate pump if gravity drainage isn't possible
5. Protect Wall Penetrations
If the hose passes through an exterior wall, seal around the penetration with a suitable silicone sealant to prevent moisture ingress — this is important under the NZ Building Code's Clause E2 (External Moisture) requirements.
What About Condensate Pumps?
If gravity drainage simply isn't possible — for example, the unit is in a basement or the drain point is higher than the indoor unit — you'll need a condensate pump (also called a mini-pump). These small electric pumps lift the water to a higher discharge point. Installing a condensate pump involves a low-voltage electrical connection, so check the pump's instructions carefully. Some plug into a standard outlet; others are wired in. If any wiring is involved beyond a standard plug, that is restricted electrical work and must be carried out by a registered electrician — see the Electrical Workers Registration Board for more information.
Common Mistakes to Avoid
| Mistake | Why It Matters |
|---|---|
| Sagging hose sections | Water pools, overflows, mould grows |
| Mismatched hose diameter | Leaks at the join |
| No hose clamps at joins | Hose pulls apart over time |
| Discharging near the foundation | Can cause moisture issues and damage |
| Forgetting to test | Always run the unit and check for leaks before closing up |
Testing Your Work
Once the extension is fitted, run the heat pump in cooling mode for 20–30 minutes and watch the entire hose run for drips, leaks at joins, or water backing up into the drip tray. Pour a small amount of water directly into the drip tray (if accessible) to confirm flow.
When to Call a Professional
Call a qualified heat pump installer or plumber if:
- You need to connect the drain to the household sanitary drainage system
- Gravity drainage isn't possible and you need a condensate pump wired in
- The indoor unit's drip tray is cracked or damaged
- You're not confident working at height (many indoor units are wall-mounted well above head height)
- The unit keeps showing a drain fault even after you've extended the hose
A qualified heat pump installer can also check that the original installation meets manufacturer specs. You can find experienced local installers on tradedirectory.co.nz.
ISO 9001
