A heat pump indoor unit (also called the wall-mounted evaporator or head unit) needs to be installed within a very small tolerance of level — typically no more than 1–2° off horizontal — to drain condensate correctly and run quietly. Checking this yourself is straightforward and requires only basic tools.
Why Levelling Matters
During cooling mode (and in some heating conditions), your indoor unit produces condensate — water that drips off the evaporator coil and collects in the drain tray at the bottom of the unit. The tray is designed with a slight built-in slope toward the drain outlet. If the unit is tilted the wrong way, water pools at the wrong end, overflows onto your wall or floor, and can cause:
- Water staining on walls and ceilings
- Mould growth inside the unit and on surrounding surfaces (a concern under the Healthy Homes Standards for rental properties)
- Gurgling or dripping noises during operation
- Premature corrosion of internal components
A unit that is also twisted (not sitting flat against the wall) can vibrate and rattle, especially at certain fan speeds.
What You'll Need
- A spirit level (a 300–600 mm level is ideal; a smartphone level app can work as a rough guide but a physical level is more reliable)
- A stepladder tall enough to reach the unit safely
- A torch to inspect the drain tray
- Optionally, a tape measure
Step-by-Step: How to Check the Level
1. Turn the Unit Off
Switch the heat pump off at the remote and at the wall isolator before getting close to it. This stops the fan and makes inspection safer.
2. Set Up Your Ladder Safely
Position your ladder on a stable, flat surface. Never lean a ladder against the unit itself — the plastic casing is not load-bearing. Follow safe ladder practices as outlined by WorkSafe NZ.
3. Place the Spirit Level on the Bottom Edge of the Unit
The bottom face of the indoor unit casing is the most accessible flat reference surface. Place your spirit level along this edge horizontally (left to right). Check the bubble — it should sit centred between the lines. Most manufacturers allow a tolerance of around 1–2° maximum off level; check your unit's installation manual for the exact specification.
4. Check Front-to-Back Tilt
Place the spirit level vertically against the front face of the unit to check whether it leans forward or backward from the wall. The unit should sit essentially plumb (vertical) front-to-back, or very slightly tilted back toward the wall as some manufacturers specify — again, refer to your manual.
5. Inspect the Drain Tray
With a torch, look up under the front louvre (the flap that directs airflow). You may be able to see the bottom of the drain tray. Look for:
- Standing water or a waterline mark at the wrong end (away from the drain outlet)
- Slime, mould, or debris blocking the drain
- Any signs of past overflow (staining on the unit's underside)
6. Check the Drain Hose Exit
Follow the condensate drain hose (usually a small flexible pipe exiting through the wall or running down to a drain). It should run continuously downhill with no upward loops (known as traps that aren't intentional). A sagging or looped drain hose can cause water to back up into the tray even if the unit itself is perfectly level.
What the Numbers Mean
| Reading on Spirit Level | What It Means | Action Needed? |
|---|---|---|
| Bubble perfectly centred | Unit is level | No action needed |
| Bubble slightly off, within 1–2° | Usually within tolerance | Check manufacturer spec |
| Bubble noticeably off (>2°) | Unit is out of level | Remounting recommended |
| Unit visibly tilted by eye | Significantly out of level | Call an installer promptly |
What You Can and Can't Do Yourself
Checking the level is a straightforward DIY task. However, remounting or adjusting the bracket is a different matter. The indoor unit is connected to refrigerant pipework, electrical wiring, and the condensate drain — all of which may need to be disturbed if the unit is moved.
- Refrigerant work is restricted work in New Zealand and must only be carried out by a person holding the appropriate refrigerant handling licence. Tampering with refrigerant lines yourself is illegal and dangerous.
- Electrical connections to the unit are also restricted electrical work under the Electricity Act and must be done by a registered electrician. Check the Electrical Workers Registration Board (EWRB) for what qualifies as restricted work.
- Adjusting the mounting bracket position on the wall (without disturbing pipework or wiring) may be possible for a competent DIYer in some situations, but given the risks of disturbing connected services, it's generally best left to a qualified heat pump installer.
Installation of heat pump systems should comply with the NZ Building Code and manufacturer specifications. If your unit was installed recently and is already out of level, contact your installer — workmanship issues may be covered under warranty.
When to Call a Professional
Contact a qualified heat pump installer or refrigeration technician if:
- The unit is more than 1–2° out of level
- You can see water overflow marks or active dripping
- The drain hose has incorrect falls or loops
- The unit vibrates or rattles against the wall
- You suspect the mounting bracket is loose or incorrectly fixed into the wall framing
A good installer will re-level the unit, check the drain fall, flush the condensate line, and confirm everything is back within the manufacturer's specification. You can find qualified local heat pump installers on tradedirectory.co.nz.
ISO 9001
