In most cases, PTFE tape is not required on compression fittings and is often unnecessary — compression fittings are designed to create a watertight seal through mechanical force alone. That said, there are a few situations where a small amount of PTFE tape can help, and understanding the difference will save you from leaks and costly repairs.
How Compression Fittings Work
A compression fitting seals by compressing a soft metal or plastic olive (also called a ferrule) against the pipe and fitting body as the nut is tightened. The seal is purely mechanical — metal-to-metal or plastic-to-metal contact under pressure. No thread sealant or tape is involved in the sealing action itself.
Common uses in NZ homes include:
- Connecting copper pipe to tapware, valves, and appliances
- Joining flexible braided hoses to isolation valves
- Connecting to hot water cylinders and dishwashers
Should You Use PTFE Tape on Compression Fittings?
The short answer: on the olive and pipe body — no. On threaded ends — sometimes yes.
Here's a simple breakdown:
| Part of the fitting | Use PTFE tape? | Reason |
|---|---|---|
| Olive / ferrule area | No | Seal is mechanical; tape can prevent proper compression |
| Compression nut threads | Generally no | Threads don't create the seal |
| Male parallel (BSP) threads on the fitting body | Yes, if connecting to a female thread | Threads need a sealant to prevent weeping |
| Male taper (NPT/BSP taper) threads | Yes | Taper threads rely on thread engagement for sealing |
The key point is that PTFE tape belongs on threaded connections, not on the compression joint itself. Wrapping tape around the olive or pipe end can actually prevent the olive from seating correctly, leading to leaks or requiring excessive tightening that damages the fitting.
NZ Building Code Considerations
All plumbing work in New Zealand must comply with the NZ Building Code, particularly Clause G12 (Water Supplies) and Clause G13 (Foul Water). Joints and connections must be watertight and durable for their intended service life. Using the correct jointing method — whether that's a properly compressed olive or PTFE tape on a threaded joint — is part of meeting that standard.
For guidance on acceptable plumbing solutions and materials, MBIE Building Performance publishes Acceptable Solutions and Verification Methods that licensed plumbers work to. If you're unsure whether a particular fitting or jointing method is compliant, check with your local council or a licensed plumber.
When PTFE Tape Is the Right Choice
PTFE tape (also called thread seal tape or plumber's tape) is the correct product for:
- Male BSP parallel or taper threads connecting to female threaded fittings (e.g., a valve screwing into a wall fitting)
- Shower arms, tap tails, and other threaded fittings where the thread itself must seal
- Gas fittings — though note that gas work is restricted work in NZ (see below)
When using PTFE tape on threads, wrap it clockwise (when looking at the male thread end) so it doesn't unravel as you screw the fitting in. Two to three wraps is usually sufficient for water; some plumbers use more on gas threads, but always follow the manufacturer's instructions.
Common Mistakes to Avoid
- Over-tightening compression fittings — this can crack the olive or split plastic fittings. Hand-tight plus about one to one-and-a-quarter turns with a spanner is a common guide, but check the manufacturer's specification.
- Reusing olives — once an olive has been compressed, it's deformed to that pipe. Reusing it on a reassembled joint often results in leaks. Always fit a new olive.
- Using PTFE tape to fix a leaking compression joint — if a compression fitting is leaking, the fix is to tighten it slightly or disassemble and replace the olive, not to add tape.
- Mixing metals without care — in NZ, mixing copper and galvanised steel can cause corrosion. Check compatibility before joining dissimilar metals.
Restricted Plumbing Work in NZ
It's important to know what you can and can't legally do yourself. Under the Plumbers, Gasfitters and Drainlayers Act 2006, most plumbing work on sanitary plumbing and water supply systems is restricted work that must be carried out by a licensed plumber.
Homeowners may generally:
- Replace tap washers and O-rings
- Reconnect a dishwasher or washing machine to an existing outlet
- Clear a blocked drain (in some circumstances)
Homeowners must not (without a licence):
- Install or alter water supply pipework
- Work on hot water systems
- Do any gasfitting work
If you're unsure whether your job is restricted, contact the PGDB or your local council before starting.
When to Call a Professional
Call a licensed plumber if:
- You're installing new pipework or moving existing connections
- A compression fitting continues to leak after careful tightening
- You're working near your hot water cylinder, gas lines, or sanitary drainage
- You're not confident identifying fitting types or thread standards
A qualified plumber will also ensure your work is compliant with the NZ Building Code and won't void your home insurance. You can find licensed local plumbers on tradedirectory.co.nz.
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