If your heat pump isn't keeping up, the most common culprit is a dirty filter or coil — not a refrigerant (gas) shortage. A proper clean fixes the vast majority of performance issues and costs a fraction of a regas. That said, refrigerant leaks do happen, and knowing the difference can save you time and money.
What a Regas Actually Means
Heat pumps operate on a closed refrigerant circuit — the gas (refrigerant) doesn't get "used up" like petrol. If your system is low on refrigerant, it means there is a leak somewhere in the system. Simply topping up the gas without finding and fixing the leak is a short-term fix at best, and is actually prohibited under NZ regulations — technicians are required to locate and repair leaks before recharging.
Handling refrigerant is restricted work in New Zealand. Only a registered refrigeration and air conditioning technician holding the appropriate licence is legally permitted to recover, handle, or recharge refrigerant. Do not attempt this yourself.
Signs Your Heat Pump Probably Just Needs a Clean
These are the most common symptoms of a dirty indoor unit:
- Reduced airflow — the fan sounds normal but you feel little air coming out
- Musty or mouldy smell when the unit runs
- Visible dust, fluff, or mould on the filter or louvres
- Unit takes much longer than usual to heat or cool the room
- Higher power bills without a change in usage habits
- Error codes related to airflow or temperature sensors (check your manual)
A blocked filter forces the unit to work harder, reduces efficiency, and can cause the indoor coil to ice up — which looks alarming but is usually solved with a good clean.
What You Can Do Yourself
Homeowners can safely:
- Remove and wash the filters with warm water (let them dry fully before reinserting)
- Wipe down the louvres and outer casing with a damp cloth
- Check that the outdoor unit isn't blocked by leaves, grass clippings, or overgrown shrubs
For a deeper clean of the indoor coil and drain tray, most manufacturers recommend a professional service every 1–2 years. This involves coil-safe cleaning agents and flushing the condensate drain — not something to skip, as a blocked drain can cause water damage to your ceiling or walls.
Signs Your Heat Pump May Need a Regas
Refrigerant issues present differently from dirt-related problems:
- Ice forming on the indoor coil or refrigerant lines even after filters are clean
- Unit blows air but it's not cold (or not warm) at all, despite correct settings
- Hissing or bubbling sounds from the refrigerant lines (possible leak)
- Unit short-cycles — turns on and off rapidly without reaching the set temperature
- Outdoor unit runs constantly but the room temperature never changes
- A technician's manifold gauge reading shows low refrigerant pressure (this is the definitive test)
None of these symptoms alone confirm a leak — a technician needs to pressure-test and check the system properly.
A Quick Comparison
| Symptom | Likely Cause | DIY Fix? |
|---|---|---|
| Musty smell, low airflow | Dirty filter/coil | Yes — clean filters |
| Water dripping indoors | Blocked drain | Partial — call a tech for drain flush |
| Ice on indoor coil (dirty filter) | Restricted airflow | Yes — clean filters, let ice thaw |
| Ice on coil (filters clean) | Possible refrigerant issue | No — call a technician |
| No heating or cooling at all | Refrigerant leak or fault | No — call a technician |
| Hissing/bubbling sounds | Possible refrigerant leak | No — call a technician |
NZ Healthy Homes and Heat Pump Maintenance
If you're a landlord, note that Tenancy Services Healthy Homes Standards require heating devices to be in good working order. A neglected heat pump that fails to meet the required heating capacity could put you in breach of these standards. Regular servicing is both good practice and good compliance.
When to Call a Professional
Call a licensed heat pump technician if:
- Cleaning the filters doesn't improve performance within a day or two
- You see ice forming on a clean unit
- You hear unusual sounds from the refrigerant lines
- The unit displays a persistent fault code you can't clear
- You suspect a refrigerant leak
Remember: refrigerant handling is restricted work — it's illegal for an unlicensed person to recharge a heat pump. A qualified technician will pressure-test for leaks, repair them, and only then recharge the system to the manufacturer's specification. For building consent requirements around heat pump installation or replacement, check with your local council — many straightforward replacements fall under Schedule 1 exemptions, but it pays to confirm.
You can find qualified local heat pump installers and service technicians on tradedirectory.co.nz.
ISO 9001
