The key differences between waterproof and water-resistant bags

“Are you looking for a waterproof bag, sir?” the sales assistant asked me. The truth is, I didn’t really know the difference. Obviously waterproof what I thought I wanted, but that posed the question - would water resistant be good enough? And what are the advantages of choosing one over the other? 

With so many bags on the market, I reasoned that it’s important to understand the difference between waterproof and water-resistant bags.

So what makes a waterproof bag?

In order for a bag to be truly waterproof, it needs to be completely free of access to water. Sounds obvious, but in fact, there are more ways for water to get in than you might think. Of course, water can get into your bag through openings (leaving the top unzipped is a good way to stop your bag being waterproof). But in fact the bigger story is that anywhere there is stitching, a small hole is created by the needle which could, in theory, let water in.

So to explain again, if there is a seam on the outside of the bag and it’s been sewn, there will be small holes that let in water. This stops the bag from being truly waterproof. These little holes act as pores and allow water to seep into the bag - albeit it usually quite slowly.

So, given that any stitching will allow water into the bag, is the idea of a waterproof bag just a myth?  

The only real way to stop a bag letting in water is not to use stitching at the seams. You can do this using a process called ultrasonic welding, which means that the bags are sealed rather than sewn. It’s a technique that fuses pieces of waterproof material together using ultrasonic waves of energy. This is pretty advanced and getting the machinery to do it is expensive. Thus, making a waterproof bag in this way adds a lot of cost to the manufacturing side of things. It follows that bags that market themselves as truly waterproof can be very expensive indeed.

Another typical feature of the waterproof bag is the roll-top. This stops water coming in at the main (and usually only) entrance to the bag. By folding over layers of material, it’s possible to create a virtually water-tight seal without using any stitching.

Waterproof bag isn't the most convenient to use.

Most 100% waterproof bags have roll tops which are usually less convenient to use.

And what about water-resistant?

In order for a bag to be truly waterproof, it will probably have to have seams that are ultrasonically welded. Most bags, however, including our own, use stitching to hold them together. That’s why they are called water-resistant. They do repel water, but they do not do it to the same extent as a waterproof bag.   

However, that’s not to say they do not use waterproof materials.

In essence, unless you make a totally waterproof bag, all you can do is try to mitigate the water coming in. And the best way to do that is to use waterproof materials. One way is to put a backing or lining on the outer material, which is why The Arcido Bag has a canvas that is lined with PVC. This creates a barrier so that water can’t go past - even though the canvas gets wet, the PVC underneath stops it getting anywhere near the inside of the bag. 

But again - to hammer the point home - even though these bags use waterproof materials, the fact that they are sewn together means that they are only ever going to water-resistant. Just like any water-resistant bag, they aim to repel water. The degree of success is determined in large part by the materials used.

For The Arcido Bag, the main thing was to use as many waterproof materials as we could in order to do the best job at stopping water getting in. To that extent, we tried to make the most waterproof ‘water-resistant’ bag we could. We lined the canvas with PVC and used waterproof zips. Overall this makes The Arcido Bag pretty effective at stopped water getting into the bag.

Arcido bag isn't 100% waterproof.

The Arcido Bag does a great job keeping water out but isn't 100% waterproof. 

Should I choose a waterproof over a water-resistant bag?

There are a lot of situations when you travel that could result in your bag getting wet. The most obvious one is rain when you’re walking around; whether that’s in a city waiting for a bus or trekking through a rice paddy somewhere exotic.

Imagine you’re in the jungle and you’re about to swim through a crocodile-infested lake. No doubt, you will want your gear to be protected; after all, you’ve got your laptop, phone, clothes, shoes - everything - inside.

But are you really planning to go on adventures that mean you will be wading through lakes or completely submerging your bag? Although many people think they definitely need a waterproof bag, usually a water-resistant one is enough. Most likely, if you’re going to be totally submerged in water you will not have your bag with you, or you will choose

The downside to totally waterproof bags

Of course, the major upside of having a waterproof bag is that it stops everything inside getting wet. But there are also some downsides to consider.

If you consider the main function of a waterproof bag is to stop water coming in, it means that the bag has fairly limited utility. You may notice that most truly waterproof bags have very few pockets and only one opening. This is because any opening, tiny or large, will increase the likelihood of water getting in. Far better to have fewer rather than more openings to the bag.

But this means that waterproof bags tend to be less functional overall. As an example, a great way to stop water is to have a roll-top opening. These are great at keeping out water but are a pain to open and close if you want something out of the bag quickly. And similarly, if no stitching on the outside is allowed, you won’t have any of the functional pockets that could be useful for storing your stuff.

We designed Arcido bags primarily as ones that we’d want to use ourselves. Our travel style tends to be more urban - quite often we are moving between urban environments; from city to airport and onto public transport. For that kind of travel, it’s perfect. Sure, it’s our bags aren’t going to withstand being submerged underwater for a great length of time but they’ll cope well with short periods of bad weather.