How to Waterproof a School Backpack | What to Use

Backpacks are essential, not only for school but also when traveling, hiking, camping or even when going to work. Therefore, getting the right one depends on the matter at hand and your sense of style.

New ones with groundbreaking features are made every other day. You might have an old pack that is durable and has served you great for years. Buying a new one to keep up with change is experimental as you might easily get disappointed. In most cases, whether trend-setting backpacks for college or school backpacks for kids or smart backpacks for your laptop or just a traveling carry on companion, they come as fully water-proof or water repellant.

Well, these kinds of packs can withstand rain and others be fully submerged in water without letting any moisture in. This is made possible by the ergonomic designs and materials used. Packed with several water-dripping inhibitors mechanisms, most are quite efficient at it. Others though aren’t as sufficient or just won’t be of any help in case of rain.

In a situation where you either don’t want to replace your beloved daypack or simply don’t have extra cash to buy a new one, learning how to waterproof one yourself will come in handy. With this guide on how to waterproof a school backpack, no more constant worries of keeping your books, documents, clothes or even your laptop dry.

Note, a water-resistant pack doesn’t mean it doesn’t allow water getting in. This only means that it doesn’t soak in water or water simply slides down and is easy to wipe off.

Well before heading into how to make one yourself, you’ll need to know the materials required. Let’s get a little technical.

What are Water-proof Backpacks Made of?

1. Polyurethane Laminate or Thermoplastic polyurethane

Polyurethane Laminate

Commonly known as PUL, this is a fabric of several uses including garments and medical purposes. It is made by laminating lightweight polyester to a 1 mil thick film of polyurethane. The laminate is breathable and stretches yet is somewhat soft and flexible enough.

It is easily washable and dried in a washing machine using bleach or alcohol severally without damage. Useful as a wind and/or water barrier comes two type cotton or polyester the latter being softer it is highly advised to keep clean after all use since it tends to disintegrate into the water and stick to itself and go moldy when wet for a long time.

Benefits of Polyurethane Laminate

  • Durable
  • Water proof
  • Flexible
  • Comfortable
  • Soft

Disadvantages of Polyurethane Laminate

  • Not as breathable as natural fibers
  • Can delaminate in extreme temperatures
  • Non-biodegradable

Thermoplastic polyurethane

Commonly known as TPU, this is tacky like material. A class of PUL but honestly a more convenient or interchangeable choice having alternating layers of hard-water proof-and soft segments. It’s more durable, softer and flexible than PUL used for the same purposes and more.

To give a better and more knowledgeable thought when choosing between the two same but not so similar compounds, here is the difference between the two with benefits and downsides.

Advantages of Thermoplastic polyurethane

  • Softer
  • More flexible
  • Less stiff
  • More durable

Disadvantages of Thermoplastic polyurethane

  • Easy breakdown, cracking and delaminating in high temperatures
  • Synthetic thus can cause sensitivity to users
  • Also not as breathable

2. Nylon and Polyester

These two aren’t water proof but are often used to make water proof materials such as umbrellas. When well coated they can act as a pretty reliable rain cover when needed. Most backpacks use these fabrics and in water-proof ones they are reinforced for capable use outdoors for rainy weather (Often called nylon taffeta and ripstop nylon.)

Ripstop nylon- this is used to make parachutes after given a water proof coating. It’s very durable and a tough fabric great tear-free quality suitable for a variety of uses.

Nylon taffeta- is a crisp, smooth, plain woven fabric made from silk coated specialy to be fully water-proof

3. Laminated Cotton

This is a type of fabric made with the same concept as PUL. Comes with a thin layer of water-proof coating for a comfortable and dry stay/feel even in extreme weather. Originated from French, the fabric is crisp and laminated with a 1 mil thick waterproof coat.

A favorite for many brands for its soft and flexible nature. It comprises of three main types: non-porous laminate, micro porous and viscous coating.

4. Oilcloth

This is something that dates back a long time. Usually prepared by boiling linseed oil with metal salts, the material is made to be waterproof. Nowadays it refers to cotton coated with a clear vinyl layer that serves the same purpose with better results.

Such hardening is durable and easy to clean without losing the water proof properties unlike the previous method applied. It has several uses like table cloths or making a garment and can work great in backpacks.

5. Waterproof Zippers

Zippers come in different designs, most are usually just water-resistant but you can get lucky and find completely waterproof ones.

How to Waterproof a Backpack – What to Use

With these easy and cheap methods, you no longer have to worry regardless of the weather. Each method works individually but combining two or more is even better.

1. Use a Seam Sealer

This is a spray used as a preventive measure. Any spray will work well if correctly used. You spray it along zippers or enclosed openings. Doing this coating using a seam sealer ensures no moisture will seep in. it’s a very cheap method and should always be done regardless of the outdoor activity.

Well, this only protects the opening but not the fabric so it goes without saying an additional method should be in place. Really cool method but won’t give you the 100 percent assurance of waterproof bag. Tip: submerging it will bring unhappy results so avoid it.

2. Use a Rain Cover

Probably the most common method out there and with good reason. Covering your rucksack using water repellant/resistant rain cover protects it fully from small drizzles and heavy storms. One of the most ingenious inventions ever, this will keep both your pack dry and your inside contents too. It was used way back and is still relevant today too.

Taking this route gives your bag a crucial first line of defense against rain. Great when walking about in the city or anywhere in the great outdoors.

Side note: being made of a thin layer of waterproof material that goes over your bag, only the back can handle submersion as the bag is not fully enclosed.

3. Use a Waterproof Backliner

Yes, lining the inside main compartment of your pack instead of putting stuff in a plastic bag first. Funny I know but a really capable method of keeping things dry. This obviously means your pack will take one for the team getting exposed to the rain and getting all wet.

Works better if openings are seam sealed, quick and easy to do even on the road. Works wonders and is very easy to clean using only reusable plastic bags. Something really good about this is that it’s good for the environment and can be used effortlessly with all types of luggage carriers and takes up little space.

4. Use a Dry Box

These are simply a heavy duty box or case designed to keep internal contents dry. Such cases are incredibly durable hence a great option for outdoor adventure. They come in all sizes and shapes and mostly used for packing fragile essentials.

Unlike plastic bags and the sort, these are strong enough to keep your stuff from getting crushed or damaged. They are usually relatively cheap and a nice way to keep important stuff nice and dry.


Doing and using any of the above methods on how to waterproof a school backpack depends on you. Sure, there’s no way you can remake your whole pack a hundred percent waterproof unless you buy one.

This according to me and my long hours of research these items are a game changer when battling extreme weather. Of course, some options may apply to a specific need. Therefore, it’s worth trying all of them out and see what fits you best.

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