Waterproof vs. Water Resistant Backpack for Bike Commuting

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To many people, a waterproof backpack can mean the same thing as a water-resistant backpack. However, that is not true. There are some major differences between the two types. But what are these differences? And which is better? To answer these questions, we have described and compared waterproof backpacks with water-resistant backpacks in this article. Keep reading to find out more.

Waterproof vs. Water-resistant Backpacks

A water-resistant backpack can prevent water from getting in but only up to a certain extent. The materials used for water resistance are so densely woven that it is very difficult for water to pass through. There are different levels of water resistance which we will talk about. In general, if a bag is water-resistant, it will protect its contents from water splashes or light rain. When faced with downpours or when submerging it, the bag will let water in.

On the other hand, a waterproof backpack is one that does not let any water inside. Even if it is fully submerged, anything inside will stay completely dry. The pores in a waterproof material are so tiny that not even water molecules can pass through. Fully waterproof backpacks also have special construction methods which we will discuss below. Beware that many brands advertise their bags as waterproof but are actually not.

Water resistant backpack
Water-resistant backpack

Water Resistant Backpacks

Materials

The most commonly used fabrics for water-resistant backpacks are nylon, cotton, and polyester. The fibers in the material are woven tightly to provide some resistance to water molecules passing through. The thickness of their fibers is expressed in denier. Generally, heavy-duty nylon such as 800D will be more resistant to water than something like 200D nylon. However, this may not always be true. Very high denier nylon might have thicker fibers but bigger gaps.

If the water pressure on the fabric is high enough, water will make its way through the material. Therefore, a coating or backing made of polyvinyl chloride (PVC), thermoplastic elastomers (TPE), or polyurethane (PU) is added. Sometimes Teflon or wax coatings are also used. These coatings make the water bead up on the surface which can roll off easily. However, over time the coating gets worn off.

Water resistant fabric
Water-resistant fabric

Construction

How the backpack is constructed is also very important for water resistance. If you check the seams, you might find stitching and needle holes through which water can get in. A common method to fortify these areas of the backpack is to seal them with silicon. Another way is to use seam taping. However, both of these can eventually get damaged or broken down. In most cases, they can last for a couple of years or so.

You should be careful of products that are marketed as “made with waterproof materials”. While the statement may be true, all the waterproof material in the world won’t make a difference if the backpack is constructed using traditional methods such as stitching and has normal zippers. So in reality, these bags are not waterproof but water-resistant.

Waterproof Backpacks

Materials

The first step to making a product waterproof is to use waterproof materials. Ideally, the material should have no holes, or at least have holes so tiny that water molecules cannot pass through. The slightest gap can let water in and the backpack can’t be called waterproof anymore. Moreover, a waterproof product should not require any sort of protective coatings.

Sailcloth is a popular choice among manufacturers due to its airtight properties. It also has several layers that can stop moisture from getting into the backpack. Other options include a thermoplastic polyurethane (TPU) and PVC, among others. These materials have the advantage of not having any pores at all.

Construction

These days, manufacturers can waterproof all parts of the backpack, including zippers. To make a perfectly waterproof backpack, you cannot sew the material. Instead, they are welded together. This is so that there are no needle holes through which water can pass. Manufacturers use one of two processes for this – ultrasonic welding or radio-frequency (RF) welding.

During ultrasonic welding, high-frequency acoustic vibrations are applied. Whereas in RF welding, high-frequency electromagnetic waves are applied. Both these processes cause the material, usually plastic, to melt and fuse together. This essentially creates a backpack made from a single piece of material. The welded area is stronger than the rest of the backpack and there are no gaps at all for liquids to enter.

What about zippers?

Zippers on a backpack are one of the main entry points for moisture. Water can seep through the teeth of the zipper. Additionally, the more zippers there are, the larger the area for water penetration. The zippers on a water-resistant backpack are typically equipped with flaps or splash guards. These are simply a piece of fabric covering the zipper teeth that shield against water reaching the zipper. A more water-resistant backpack will have coated zippers. These seal up almost completely when closed.

Zippers that are 100% waterproof are different from the water-resistant zippers mentioned above. They are much better at keeping water out, require more maintenance, and are quite expensive. Some brands advertise their backpacks as having “waterproof zippers”, but beware. If the product is sewn, the zipper is likely to be water-resistant only. After all, pairing a very high-end zipper with cheaper water-resistant construction would make no sense.

Water resistant coated zipper
Water-resistant coated zipper

The IP Code: Measuring water resistance level

The Ingress Protection Code, or IP Code for short, is an international standard for classifying the level of protection a product offers against intrusion from water and other things such as dirt and dust. Each product with an IP code is labeled with two digits side-by-side. The first number indicates the level of protection from dust/dirt, rated from 0 to 6. The second digit is for protection against water and is rated from 0 to 9.

For example, a backpack with an IP62 rating provides complete protection from dirt and dust but does not stop water very well. Conversely, a product rated IP19 offers almost zero protection from dust but can handle a high water pressure and can even be immersed up to depths of 1-3 meters in water. Therefore, if you want a backpack with very high water resistance, look for an IP rating with the second number being 9 or close to 9.

Frequently Asked Questions

Q1. How do I choose between a waterproof and a water-resistant backpack?

Ans.: If you want a backpack for everyday use or doing activities where your biggest concerns are splashes and light rain, then a water-resistant backpack is more than sufficient. For places with heavier rainfall, look for a good quality backpack with a high level of water resistance. You will need a truly waterproof backpack if you are doing something like white water rafting or hiking through waterfalls where there is a high chance of submersion.

Q2. What are the downsides of a waterproof backpack?

Ans.: The main disadvantage of a waterproof backpack is its limited utility. Stopping water from coming in, which is its main function, requires the backpack to have a small number of outer pockets and just one main opening. This gives waterproof backpacks low functionality when it comes to everyday use. For instance, many of them have a roll-top opening, which is great for stopping water but does not open and close as quickly as a zipper. Moreover, waterproof backpacks are a lot more expensive.

Waterproof backpack with a roll top opening
Waterproof backpack with a roll-top opening

Conclusion

To be perfectly honest, more than 90% of people will never need a fully waterproof backpack. For most people, especially cyclists, the main concern is protection from the rain. And there are plenty of high-quality water-resistant backpacks out there. Many of these can hold up against heavy rainfall for a decent amount of time. So think about your requirements and buy a backpack accordingly.

My name is Dion Lewis. I’ve been cycling since my childhood. When I was in high school, I started racing in our local competitions. In my college life, I took a part-time job in a bicycle shop and I learned how to repair and maintain bicycles professionally. Though I love racing, mountain biking is another thing I do frequently. My friends, neighbors, and colleagues treat me as an avid rider and take my suggestions while they plan for a new bike or bike gear.

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