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DWR 101: An Introduction to DWR + Outerwear Waterproofing

By Chris Pew on

So you want to know more about DWR, eh?

Well, you've come to the right place. As designers and purveyors of technical outerwear, we consider ourselves here at TREW to be experts in the subject. And while the topic of DWR, and waterproofing as a whole, can be quite complicated - especially with the ever-changing landscape around industry standards in sustainability - we've taken a moment to break down the basics behind Durable Water Repellents (DWR) and how us them in TREW products.

What is DWR and how does it work? 

DWR is an acronym for “Durable Water Repellent” and is the surface coating that is applied to much of the outdoor clothing, tents, and gear that you use. The DWR coating is applied in an ultra-thin layer to the surface of the fabric.

The goal of DWR is to shed moisture and it achieves this by forming a protective layer of tiny, rigid microscopic bristles that don’t allow water droplets to grab onto the surface of the fabric. Instead, the tiny droplets of water roll across this microscopically textured surface and never actually come into contact with the woven fabric. To us, this looks like water beading off the surface of the fabric, and it is a highly desirable function for outdoor gear. Without a DWR coating, this level of water repellency wouldn’t be possible for the vast majority of outdoor gear and apparel. 

Does the kind of fabric/membrane under the DWR coating really matter, then?

Absolutely. The DWR coating is just your first line of defense. A DWR coating is neither windproof nor inherently waterproof, it cannot withstand water pressure like a waterproof membrane. Furthermore, no DWR coating is permanent; it will degrade over time and it is the characteristics of the woven fabric and membrane that will keep you dry over many years of use. In a waterproof/breathable laminated fabric, it is really the combination of DWR, woven fabric, and membrane that keep you dry and comfortable. 

So, what’s the problem with DWR?

Most of these DWRs are built with fluorocarbon chemistry, in particular, perfluorocarbons (known commonly as PFCs). They are very good at creating long-lastingly repellent surfaces, but, on the other hand, they are also very good at not breaking down in the environment. The toxicity of PFCs to humans is largely unknown - but the threat, in summary, is that once they are in the environment, they are extremely hard to remove and they basically never degrade, making them a potentially constant presence in our food and water supply. 


The term PFC has historically referred to two classes of chemicals: perfluorinated chemicals and perfluorocarbons (often just called fluorocarbons). Perfluorocarbons are a subcategory of perfluorinated chemicals, and are chemically different from the famously toxic perfluorinated chemicals: PFAS, PFOS, and PFOAS (generally also referred to as polyfluoroalkyl substances, PFAS).   

These PFAS are the same chemicals that go into nonstick cookware and many other household products. This has historically come as a shock to most outdoor aficionados, but Gore-Tex and Teflon are cut from the same chemical cloth: PTFE - and both have traditionally used the perfluorinated chemical, PFOA, to create their nonstick or repellent surfaces. PFOA-free versions of Gore-Tex and Teflon have only recently become available. 

PFOAS, specifically, are known to be toxic to humans. They are linked to everything from general immune deficiencies to cancer. They are incredibly persistent in both the human body and the environment and should be avoided whenever possible. There are no PFOAS in any TREW products. 

>> Read more about PFAS and recent Regulatory Updates. <<

C8 vs. C6 DWR

The most common DWR coating in the past several decades is a version of DWR chemistry called C8 or “long-chain.” This C8 chemistry did, in fact, contain PFAOS, and was known to be toxic. C8 was effectively banned by the EPA in 2016 (to read a long, depressing, article about the lawsuit against DuPont, here’s the nytimes story). 

All manufacturers of DWR coatings adopted a shorter-chain DWRs, known as C6. C6 chemistry is far less bioavailable to humans and similarly less-persistent to the environment. While C6 chemistry is known to be less harmful to humans and the planet than C8 chemistry, it is not a viable long-term alternative and we will continue to test safer alternatives.

Are there eco-friendly alternatives?

Fortunately, yes! There have been many advances that have led to some great performing eco-friendly DWR treatments. These treatments are commonly referred to as C0, as they contain no fluorocarbon chemistry. 

We use Empel’s innovative C0 DWR on our Snap Jack and PDX Jack, for example. The performance of many of these options are adequate for many different applications, and sometimes even better than a traditional DWR. 

However, today, for laminated fabrics like the waterproof fabrics that we are using, there is a steep enough decline in performance of C0 options as to give us pause for full integration in our most waterproof and durable product lines. 

TREW’s DWR policy:

We will only use C6 DWR if it is absolutely critical to the performance and longevity of the garment.* Today, we only use a C6 DWR finish on the shell fabric of our most rugged 2-layer and 3-layer outerwear garments. All “sub fabrics,” powderskirts, pant gaiters, internal facing fabrics, etc, are treated with either C0 DWR or no DWR at all.   

For any non waterproof garment where waterproofing isn’t critical for performance or inherent in the construction of the fabric – like insulated midlayers, knit base layers, and wind jackets – we either leave the fabrics uncoated or use a C-0 DWR.

We are constantly testing new PFC-free DWRs and will continue to evaluate them as a better alternative to C6 DWR coatings. Our goal is to find a solution that doesn’t needlessly add potentially harmful chemicals to the environment while also ensuring that our products can achieve lasting performance and durability.

Why is DWR critical for some shell fabrics? 

We use a (PFOA-free) nonporous polyurethane membrane on our waterproof outerwear. These PU membranes are easy to care for, durable, and offer uncompromising wind and waterproofing. But in order for the membrane to function properly, the outer fabric must repel water - and the first and most important line of defense is the DWR coating. If the outer fabric gets saturated with moisture, the membrane won’t be able to push your body’s vapor to the exterior of the fabric and the inside of the fabric will become uncomfortably moisture-laden. 

This leads to the phenomenon of “wetting out,” where the membrane becomes overwhelmed with moisture from both the exterior and interior of the fabric and is no longer an effective waterproof or breathable barrier. 

It’s also important to note that this is only in the extreme situation where the outer fabric has zero water repellency, and that a DWR coating is not the only thing that repels water or moisture. The shell fabric itself will have inherent weather proofing properties. At TREW, we prioritize using woven fabrics that are densely woven and durably constructed to enhance their inherent water repellency and prolong the longevity of the garment. 

Proper (and regular!) care and cleaning of the outer shell fabric is another way to protect the repellency of the fabric and functionality of the garment, as well as periodic use of a reproofing product to reapply the DWR coating once the original has worn down.

Worried about PFAs and PFCs? Here’s what you can do. 

Immediate steps that you can take is to take a look at all of the products that you buy and look for safer alternatives. Household products like non-stick pans, cleaners, or any nonstick treatments tend to use PFAs. There are also many apparel products that don’t need to be critically waterproof that use DWR treatments to market themselves as water-resistant. If your khaki pants are advertising that they are water and stain resistant, take a close look at the additives that give them that special performance. The same can be said for lots of outdoor gear. Does your puffy or fleece products need a PFC-laden DWR? Probably not.

Looking to minimize the proliferation of PFCs in our environment and your own surroundings? We’d love to hear from you. Our mission is to build apparel that meets the needs of our customers and we’d love to know your priorities.

Customer FAQ

Q: My last ___fill in the brand name here____ jacket lasted for 15 years and I never had any issues with waterproofing or needing to reapply a DWR coating? Why isn't my new TREW jacket living up to this?

A: Nothing repels water (and oils and grease) like a nice thick coating of Teflon, but, fortunately for our planet, the glory days of long-chain DWRs are behind us. The new coatings are not as robust and require more care.  

Q: I bought a pair of TREW bibs two years ago and have about 45 days on them. I have noticed that the waterproofing is starting to go, and the fabric is starting to look wet - and sometimes I feel like there is moisture getting through the fabric. What is going on, and what do I do to fix this?

A: The DWR coating is your first line of defense against your fabric wetting-out but it cannot withstand continuous downpour or, more commonly, is easily compromised by dirt and oils on the surface of the fabric. If the outer fabric on your jacket is wet, there is nothing to be alarmed about and is often the price that we pay as skiers and snowboarders in the PNW. It is important to take careful note of how you are layering and managing the moisture building up on the inside of your shell. When your shell fabric is saturated it can no longer push your body's moisture to the exterior, essentially shutting down the breathability and causing a lot of moisture to build-up on the interior. It can be really uncomfortable and cold. Keep yourself dry by keeping your shell clean and wear the appropriate layers. 

Q: I was always told that I wasn't supposed to wash technical fabrics because it was bad for the waterproofing. Is this true?

A: This used to be true for many microporous fabrics. But that's why we use a nonporous membrane. Our fabrics LOVE to be washed and they LOVE to be dried. It keeps the surface of the fabric clean and helps the DWR chemistry get workin'. 

Q: Why do I need to heat dry my outerwear? I was always under the impression that, if washed or wet, you should hang dry to keep the technical properties of the garment intact.

A: Well, you're wrong. Don't fear the dryer! Our gear can handle it. The heat of the dryer actually helps reactivate the chemistry of the DWR, reestablishing that surface tension that you need to repel water.  

Q: In terms of gear care products, what would you recommend for keeping my TREW items in tip-top shape?

A: While NikWax and Gear Aid products do work well in most cases, we have found that Grangers products work the best and provide a great system to keeping your outerwear clean and performing at its best.

Everyone uses their gear differently, so it's tough to give a straight answer on how often or regularly one person might need to wash + dry or reapply a DWR coat to their gear (ex. someone who is a bit harder on their gear will need to wash more frequently) - but in general, here is the rundown on what grangers product will be best for whom:

  • Grangers Wash + Repel 2-in-1 is great for someone who regularly takes care of their garments (i.e. don’t let them get nasty before washing) and who want a quick, easy way to take care of them on an ongoing basis. This has the same DWR application as Grangers' other products, but the cleaning portion is slightly more gentle.
    • At a certain point, you may want/need to apply a new DWR coating with the Repel Plus spray-on, but you will typically find that regular washing with 2-in-1 will keep your original DWR lasting longer than with irregular washing.
  • Grangers Performance Wash, followed by the Repel Plus DWR spray when needed, will be a great option for someone who cleans their gear less frequently and typically waits for the performance of the item is starting to lack. This combo is the best, most focused way to get the most effective clean followed by the most effective proofing. A dedicated wash cycle is best to treat soiled garments, and you will want to do a complete wash + dry cycle with the Performance Wash before moving on to the instructions on the Repel Plus. This process takes slightly more time, but I recommend this way for people who are more “serious” about their gear care. One of our most popular gear care products is the Grangers Clothing Care Kit, which includes all that you need for this option.
    • There are options out there for wash-in DWR coatings, but we strongly recommend opting for the spray-on versions as this allows you to keep the DWR on the areas that need it most, effectively coating the outer shell + focusing on high-abrasion areas (shoulders, waist, knees, etc.).
    • Additionally, you don’t need to reapply DWR after each wash, contrary to popular belief. Grangers Performance Wash is effective at cleaning, but won’t strip DWR coating. From new, you can probably wash a garment 3-5 times at least before having to reapply DWR, depending on use of course.

Not finding an answer to your questions above? Or want to chat with us about your gear, DWR, waterproofing, or anything else? We're here to help - just get in touch with us at

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