Waterproofing Terms Explained — What They Actually Mean

Waterproofing Terms Explained — What They Actually Mean

Jacket marketing is full of numbers and acronyms that sound impressive but don't tell you much without context. Here's a plain-English breakdown of what the key waterproofing terms actually mean — and why they matter for tramping in New Zealand, where the weather doesn't care about your plans.

Hydrostatic Head (HH)

Hydrostatic head measures how much water pressure a fabric can resist before it starts leaking. The test works by standing a column of water on top of a fabric sample — the number refers to how tall that column gets (in millimetres) before water pushes through.

• 1,500mm: Water-resistant. Fine for light drizzle, not much else.
• 10,000mm: Waterproof. Adequate for moderate rain and most tramping conditions.
• 20,000mm+: Serious waterproofing. What you want for sustained heavy rain, exposed ridgelines, or multi-day trips in alpine terrain.

For NZ conditions — particularly in Fiordland, the Westland, or the Southern Alps — a minimum of 15,000mm HH is worth targeting. The West Coast doesn't mess around.

DWR — Durable Water Repellency

DWR is a coating applied to the outer face fabric of a waterproof jacket. It causes water to bead up and roll off rather than soaking into the fabric. It's not the waterproof membrane — it's the first line of defence that keeps your jacket working the way it should.

DWR degrades over time through use, washing, and UV exposure. When it fails, water no longer beads — it spreads across the fabric and soaks in (more on that under "wetting out" below).

You can restore DWR treatment with a product like Nikwax TX Direct, which is applied after washing and reactivated with low heat. It's worth doing every season or whenever you notice your jacket isn't shedding water like it used to.

Waterproof vs Water-Resistant vs Water-Repellent

These three terms get used interchangeably in marketing. They're not the same thing.

• Water-repellent: Has a DWR coating. Beads water in light rain. No membrane. Not waterproof.
• Water-resistant: Resists penetration to some degree — typically tightly woven fabrics or light coatings. Good for a brief shower. Will eventually wet through.
• Waterproof: Has a bonded membrane (or coating) that blocks water penetration, plus seam sealing. Actually keeps you dry in sustained rain.

A waterproof jacket has all three working together: DWR on the face fabric, a waterproof membrane in the middle, and sealed seams. Remove any one of those and it becomes something less.

Seam-Sealed vs Taped Seams

Even a waterproof membrane leaks at the stitching. Every needle hole is a potential entry point. Seam taping fixes that.

• Critically taped: Only the high-exposure seams (shoulders, hood) are taped. Fine for casual use in mild conditions.
• Fully taped: Every seam is taped. Required for serious weather, extended trips, or alpine conditions.

If you're tramping anywhere with real weather exposure, look for fully taped seams. Critically taped is a cost-cutting compromise that shows up in lighter-duty jackets.

Breathability — MVTR and RET Explained

A waterproof jacket that doesn't breathe turns you into a sauna when you're working hard. Breathability is about letting water vapour (sweat) escape from inside the jacket while keeping liquid water out.

Two main measurement systems:

• MVTR (Moisture Vapour Transmission Rate): Measured in grams per square metre per 24 hours. Higher is better. 10,000g is moderate; 20,000g+ is good; 30,000g+ is excellent.
• RET (Resistance to Evaporative Transfer): Measures resistance to vapour transmission. Lower is better. RET under 6 is excellent; 6–13 is good; 13–20 is moderate.

For aerobic tramping — carrying a pack on steep terrain — breathability matters as much as waterproofing. A jacket that keeps rain out but traps all your sweat leaves you just as wet.

Gore-Tex vs Proprietary Membranes

Gore-Tex is a brand name for a specific type of ePTFE (expanded polytetrafluoroethylene) membrane. It's well known, well tested, and comes with a guarantee from the manufacturer. There are several variants for different performance levels.

Plenty of other companies make their own waterproof membranes — eVent, Pertex Shield, HyVent, OutDry, and others. Some perform comparably to Gore-Tex at a lower price point; some don't. The key specs to compare are HH rating, breathability (MVTR or RET), and seam taping — not just the brand name on the label.

A proprietary membrane with good specs isn't automatically worse. But Gore-Tex does have strict licensing requirements that enforce quality standards across the garments that use it.

Wetting Out — What It Is and How to Fix It

"Wetting out" is when the outer face fabric of your jacket stops shedding water and starts absorbing it. Instead of beading, water spreads into the fabric and creates a clammy, cold feeling — even if the membrane is technically still keeping water out.

This happens when the DWR coating degrades. The membrane underneath might be fine, but the saturated face fabric blocks breathability, adds weight, and makes the jacket feel cold and wet to wear.

The fix: wash the jacket (follow the care label), then apply a wash-in or spray-on DWR restorer. Nikwax TX Direct is the standard recommendation. After treating, dry on low heat — warmth helps reactivate the DWR chemistry.

If your jacket is wetting out regularly, it's worth checking whether the face fabric is starting to delaminate — that's a different problem that DWR treatment won't fix.

Browse rain jackets at Dwights — or check out the Peak XV Tornado jacket ($299.99) as a solid benchmark for fully taped, high-HH construction in a NZ-ready shell. For DWR treatments, see our clothing treatments range.

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Frequently Asked Questions

What hydrostatic head rating do I need for tramping in New Zealand?

For most NZ conditions, aim for at least 15,000mm HH. For alpine areas or multi-day trips in high rainfall zones like Fiordland or the West Coast, 20,000mm+ is better. 10,000mm is adequate for mild conditions but can fall short on a serious storm day.

What's the difference between waterproof and water-resistant?

A waterproof jacket has a bonded membrane and sealed seams that block water penetration in sustained rain. A water-resistant jacket may resist light drizzle due to tight weave or a light coating, but will wet through in heavier or prolonged rain. They're not interchangeable.

How do I restore the DWR on my jacket?

Wash the jacket first according to the care label, then apply a DWR restorer like Nikwax TX Direct (wash-in or spray-on). Dry on low heat to activate the treatment. This is worth doing at the start of each season or whenever you notice water spreading rather than beading on the fabric.

What does "wetting out" mean?

Wetting out is when the outer fabric of a waterproof jacket becomes saturated — water spreads into the face fabric instead of beading off. It happens when the DWR coating wears down. It can make the jacket feel cold and heavy and reduces breathability, even if the membrane underneath is still working.

Should I get fully taped or critically taped seams?

For any serious tramping — multi-day trips, alpine terrain, exposed conditions — fully taped is the better choice. Critically taped seams cover only the main shoulders and hood, which leaves other seams as potential leak points in heavy, sustained rain.

Does a higher MVTR number mean a jacket breathes better?

Yes. MVTR measures how much water vapour can pass through the fabric in 24 hours — higher numbers mean more breathable. For active tramping, look for 20,000g/m²/24hr or above. Below 10,000g you'll likely feel clammy on steep, hard efforts.

Are proprietary waterproof membranes as good as Gore-Tex?

Some are, some aren't — it depends on the specific product. Compare the actual specs (HH rating, MVTR/RET, seam taping) rather than relying on brand name alone. Gore-Tex has licensing standards that ensure a quality floor, but well-specced proprietary membranes can perform just as well at a lower price.