EQUIDRY create the best waterproof coats and jackets for horse riders

What Does a 20,000mm Waterproof Rating Actually Mean?

Walk into almost any tack shop or browse online and you'll see jackets described as waterproof, highly waterproof or stormproof.

But what do those words actually mean?

The truth is that "waterproof" isn't a regulated marketing term. A jacket can legally be described as waterproof without telling you how waterproof it really is.

At EQUIDRY, we believe riders deserve more than vague claims. We exist to create the best waterproof coats and jackets for horse riders, equestrians and anyone who spends their time outdoors, using science, innovation and real-world testing to deliver waterproof performance you can rely on.

Every performance fabric we use is independently laboratory tested by SGS, one of the world's leading testing organisations, to verify key performance standards including waterproofness, breathability, strength and durability.

But laboratory testing is only where the process begins.

Before any garment reaches production, it spends months being worn, ridden in and put through its paces by our team in real-world equestrian conditions. From long days in the saddle and wet winter yard work to dog walks, competitions and everyday riding. Every design is refined through extensive field testing to ensure it performs exactly as we claim.

Because the best test isn't just in the laboratory, it’s how a garment performs when real riders depend on it.

Only once we're confident a garment performs in the real world do we put it into production.

So, when we say a coat is 20,000mm waterproof, what does that actually mean?

The simplest way to compare waterproof clothing is by understanding hydrostatic head.

What is Hydrostatic Head?

Hydrostatic Head is the internationally recognised laboratory test used to measure how waterproof a fabric really is.

Rather than relying on opinion or outdoor demonstrations, the test measures exactly how much water pressure a fabric can withstand before water begins to penetrate through it.

The result is given in millimetres (mm).

The higher the number, the greater the waterproof protection.

For example:

Waterproof Rating	What it Means
1,500mm	Minimum level often described as waterproof. Suitable only for light showers.
5,000mm	Moderate rain for shorter periods.
10,000mm	Heavy rain and general outdoor use.
20,000mm	Premium waterproof performance designed for prolonged heavy rain.

At EQUIDRY, the majority of our waterproof technologies are independently tested to achieve over 20,000mm waterproof protection.

How is Hydrostatic Head Tested?

The Hydrostatic Head test is carried out in a laboratory using specialist equipment.

A sample of fabric is securely clamped beneath a sealed cylinder.

Water pressure is then increased gradually against one side of the fabric.

The moment three droplets of water penetrate through the fabric, the pressure is recorded.

That measurement becomes the waterproof rating.

For example:

If water penetrates at 20,000mm, the fabric receives a waterproof rating of 20,000mm Hydrostatic Head.

Because this is a laboratory test carried out under controlled conditions, it allows different fabrics to be compared fairly and consistently.

Why Does This Matter for Riders?

Water pressure isn't created only by rain.

Everyday riding places additional pressure on waterproof clothing.

For example:

Sitting in a wet saddle.
Leaning against stable doors.
Carrying haynets.
Wearing a backpack.
Kneeling in wet grass.
Resting your arms on soaked fences.

Each of these activities increases the pressure pushing water against the fabric.

A jacket with a lower waterproof rating may cope with a shower but begin to leak when pressure is applied.

A higher Hydrostatic Head gives the fabric a much greater margin before water can penetrate.

How EQUIDRY verifies Waterproof Performance

Waterproof protection is only one part of a high-performance garment.

To ensure every EQUIDRY technology delivers reliable performance in demanding equestrian conditions, our fabrics undergo a comprehensive programme of independent laboratory testing. Rather than relying on a single waterproof test, we assess every characteristic that contributes to long-term performance, comfort and durability.

Testing includes:

Hydrostatic Head – Measures how much water pressure the fabric can withstand before water penetrates.

Water Vapour Transmission – Measures how effectively moisture vapour escapes, helping regulate body temperature.

Martindale Abrasion Resistance – Measures resistance to wear caused by repeated rubbing and friction, simulating years of everyday use.

Tear Strength – Assesses the force required to tear the fabric, ensuring it can withstand demanding conditions.

Tensile Strength – Measures the overall strength of the fabric under tension.

Seam Performance – Evaluates the strength and stability of stitched seams under load.

Colour Fastness – Tests resistance to fading, washing, rubbing, water and perspiration to ensure garments retain their appearance over time.

Spray Testing (DWR Performance) – Evaluates how effectively the Durable Water Repellent (DWR) finish causes water to bead and roll off the fabric surface.

Fibre Content Verification – Confirms the fabric composition matches our technical specification.

Every test provides another piece of the performance picture, ensuring our garments don't just keep the rain out on day one, but continue to perform through years of riding, yard work and everyday outdoor use.

Many of our fabrics also undergo repeated wash testing to verify that waterproof performance, breathability and water repellency are maintained after laundering, ensuring long-term performance rather than just new-garment performance.

Waterproof Doesn't Mean Comfortable

Many people assume waterproof is the only thing that matters.

It isn't.

Imagine wrapping yourself in a plastic bag.

Rain stays out…

…but so does heat.

Sweat and moisture become trapped inside.

You feel wet even though rain hasn't penetrated the jacket.

This is why waterproof clothing also needs to be breathable.

A waterproof membrane should stop rain entering while allowing water vapour created by your body to escape.

(We'll explore breathability in more detail in our dedicated guide.)

Why We Chose 20,000mm

Could we sell jackets with lower waterproof ratings?

Yes.

Many brands do.

But equestrians don't stop when the weather turns.

They ride through driving rain, stand on windy showgrounds, muck out in winter and spend hours outdoors regardless of the forecast.

That's why we've built the majority of our waterproof technologies around 20,000mm+ waterproof protection, giving riders confidence that their clothing is designed for the realities of equestrian life, not just the occasional shower.

Waterproof Ratings Don't Tell the Whole Story

Hydrostatic Head is one of the most important indicators of waterproof performance.

But it's only one piece of the puzzle.

The best waterproof jacket also depends on: