How to Waterproof a Backpack

We understand how frustrating it is to have soaking wet gear. Even if you’ve purchased a new backpack with the intention of never taking it camping, hiking, or kayaking, it doesn’t hurt to waterproof it. You never know when your water bottle decides to spring a leak, or you accidentally spill coffee on your new backpack.

Before you take your backpack on any excursion, take a few moments to waterproof it. You’ll appreciate the effort, especially if you have an unfortunate water-related accident. Waterproofing a backpack is easy! Here, we’ll show you how.

Why You Need to Waterproof Your Backpack

If you are an avid hiker, camper, or kayaker, it’s in your best interest to waterproof any gear that might go with you on an outdoor adventure. You also benefit from waterproofing your backpack if you walk to work and get there despite the weather.

Yes, you can buy insulating materials that claim to keep the gear in your backpack dry. But nothing replaces the easy steps of waterproofing your backpack.

Just think how miserable it is having a soaking wet coat that you plan to wear outside. If it gets wet in your backpack, it’s useless to you until it dries. If you’d waterproofed your pack, you wouldn’t have to wait! Waterproofing your backpack can help keep you dry and warm.

Methods of Waterproofing Your Backpack

You have several options for waterproofing your backpack. For proper waterproofing, you should combine some methods. Most of them alone will provide water-resistance, which means that rain will stay out of your pack, but your gear gets wet if your backpack is submerged. We have a full writeup on the differences between waterproof, water resistant, weatherproof, and a bunch of other terms.

When you make your backpack water-resistant, you protect your gear in light rain or drizzle. Your backpack might get slightly wet, but the items inside will stay dry. Waterproofing your bag keeps everything dry, even if your pack is completely submerged.

Spray and Seam Sealer Method

Seam-sealing and spraying can add water-resistance to a backpack. To seal and protect your pack, use a spray or wax sealant. By rubbing a seam-sealing wax on the seams and stitching, you moisture-proof the inside of your backpack. Cover the seams on the outside and inside of your bag.

This method does not add extra weight to your backpack, but it can be helpful if you aren’t planning on taking your pack near bodies of water or in pouring downfalls. If you use a spray, you can get the job done faster and spray it all over your backpack. If you use a sealing wax, you have to apply it by hand by spreading it evenly on the seams.

Silicon sprays will provide water-resistant protection to a backpack. Before you fully cover your backpack with a spray, do a test strip to see if the spray discolors your backpack. Boiled linseed oil also provides water-resistance. While silicon sprays and boiled linseed oil make the fabric waterproof, the seams and zippers will allow water to seep inside.

To make your backpack truly waterproof, spray the fabric, seal the seams, and add a secondary form of protection like a dry bag or rain cover.

Steps for Seam-Sealing

  • Empty everything from your backpack
  • Apply the seam sealer directly to the seams on the outside
  • If using a spray, apply the spray sealer all over the backpack
  • Let the backpack dry
  • Turn the backpack inside out
  • Apply the seam sealer directly to the seams on the inside of the backpack
  • Spray the inside of the backpack
  • Let the backpack dry

Use a Rain Cover

The seam-sealing method adds a minimal level of protection. You can add extra protection when you use a pack cover.

If you are looking for a lightweight form of water protection in heavier rain, a rain cover works. These lightweight covers stretch over backpacks. Because the covers are made of nylon or another naturally waterproof material, your backpack will stay dry.

You don’t have to cover your backpack with a rain cover permanently. Instead, keep the compact cover folded in a pocket so you can quickly access it and cover your pack when the rain starts.

Unfortunately, rain covers often slide off of backpacks, especially when the wind picks up. You can prepare yourself for this problem by attaching your rain cover with a carabiner or hook and loop closure. You might have to do some customization work, so be sure you don’t leave any gaping holes that could get your backpack wet.

Rain covers for backpacks are not universally sized, despite what labels might say. Many rain covers are too big for most backpacks, so check them out before you are forced to use them. If your rain cover is too big, use waterproof glue to double up your cover and add hook and loop closures to attach it to your backpack.

Add a Pack Liner

Rather than protecting the exterior, you can use a pack liner to protect what’s on the inside. A backpack liner is a large plastic bag, like a dry bag, that keeps your items dry. When you keep things in a pack liner, your backpack can get wet, but your gear won’t. You fill the pack liner, then put it in your backpack.

While this might seem like the best choice for waterproofing your backpack’s gear, pack liners are prone to tearing. To protect your gear and your pack liner, you want to get all of the air out of your pack liner. After you’ve filled it, squeeze out the air, close the pack, and create a seal by folding the top and securing it with a rubber band or clip. Keep sharp objects out of it.

When shopping for a pack liner, you can buy some specifically made for backpacks. Or you can buy a dry bag and use it as a pack liner. Dry bags cost more, but they will keep your gear dry – even if you drop it into a body of water. Dry bags are more durable than pack liners.

The biggest problem with using a pack liner or a dry bag in your backpack is that neither protects the outside of your pack. You can pair a pack liner with a rain cover and hope that both work flawlessly.

Save Money with a Garbage Bag

If you prefer to spend money on other things, you can put a garbage bag to use on the inside and the outside of your backpack. You can cover your backpack with a garbage bag, especially one with built-in tie closures. If your garbage bag is big enough, you might be able to use a strap or two to carry it.

If you don’t mind the lack of breathability and the ridiculousness of it all, you can also wear a garbage bag over your body, like a rain poncho. Heavy-duty 50-gallon garbage bags can cover your body while you are carrying a backpack. Cut a hole in the bottom and slide the bag over your head. For added protection, cover your backpack with a second bag while you are wearing your garbage-bag rain poncho.

You can also use a garbage bag on the inside, just like you would a pack liner. Just remember that garbage bags tear easily. You might want to use two or three garbage bags for protection from tears.

Protect Small Items with Ziploc Bags

If you aren’t worried about your backpack getting wet, but you want small items to stay dry, put them in individual Ziploc bags. Resealable plastic bags keep matches, earbuds, and smartphones dry. The small bags don’t add any extra weight, so keep extras in your backpack.

Unfortunately, plastic baggies wear out quickly. If you are opening and closing them frequently, keep extras with you. Instead of resealable baggies, you can also turn to 2mm poly bags, but you have to buy them in bulk.

Remember, like garbage bags, resealable plastic baggies are not environmentally friendly. They do not last long, so you will end up throwing them in the trash, where they will end up in landfills. 

Invest in a Dry Bag

If you are in a situation where your backpack could become submerged, we definitely recommend investing in a waterproof dry bag. These bags are completely waterproof, as long as you close them according to the directions. They tend to be a bit heavier since they are made with denser material.

When you put your backpack in a dry bag, you will not be able to wear your backpack. Instead, you’ll have to carry your dry bag. To keep items dry, they have very few seams, so they tend not to have handles. You could attach a rope with a carabiner and carry your dry bag over your shoulder if you are out hiking.

The Last Drop

Overall, dry bags are only convenient if you have to bring your backpack on a boat. With a little seam sealing and a few plastic liners or baggies, you can keep your gear dry. As most plastic items are not environmentally friendly, use them in moderation and try to reuse them as much as possible.

If this sounds like it’s right up your alley and you’d rather just shell out for a new backpack, check out our top picks for waterproof backpacks, all tested by us.