Dry Bag Leak Testing

Inspired by a post at another paddling site, I decided to leak test my dry bags. I weighted the bags with a small dumbbell, sealed the tops and kept the roll-top above water line, and then placed them into a bucket of water for 10 mins. I was disheartened by the results.

Sea to Summit e-Vent “waterproof” cordura compression sack: never exposed to water, used maybe 3 times for backpacking: noticeable dampness but no large puddles of water at the bottom

Sea to Summit 4 liter Ultra-sil dry sack: similar results to above. Also never abused through aggressive use.

Multiple size iterations of Eastern Mountain Sports (Cascade Designs) Baja bags. 14 + years old, rubber texture. Of the 3 I had, all but one had significant leaks = a cup or more of water in the bottom. The third one remained bone dry.

Eastern Mountain Sports small, clear bags. Not sure who the manufacturer was. Also 14+ years old. Significant leaks.

I expected the old bags to have issues. They saw a lot of use, getting stuffed in and out of hatches, during my first foray into paddling and perhaps being stored away for years caused folds and cracks in the material. I didn’t expect the newer StS bags to be damp inside. It reminded me of when you ‘wet out’ a gortex rain jacket, that damp but not saturated feeling. Not confidence inspiring since I planned to keep clothes in them.

Somewhere (Kayak Academy?) I read that the newer nylon bags are both lighter, easier to pack into hatches and just as waterproof as the old rubber bags. I’m not sure about that…

Take home message: leak test your bags at the start of the season.


I regard all roll top dry bags as “semi-dry” at best. I haven’t found any that can be counted on to be completely dry after full immersion, especially full immersion in current.

On the other hand, a smaller dry bag inside a slightly larger one will usually keep the contents of the inner bag dry.

If I want to be relatively sure that something will stay dry I put it in a Watershed dry bag or duffel.

The closure system is the weakest link, for sure. That’s why I kept the tops of the bags well-above the waterline. So any moisture in the bags came in through the seams or the fabric itself. My guess is that the nylon fabric is “waterproof” to the extent that if it made temporary contact with water (splashed for example) it would repel the water, whereas it cannot withstand immersion for ten minutes in a bucket.

I suppose if they were sealed in a kayak hatch, that level of water resistance might be enough provided the hatch seals and the hull are competent.

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I have used the event compression bags for 10-years without a problem in my kayaks and longer in my backpacks. In a canoe the smaller bags go into a larger bag or large plastic container. I use aqua seal on any pinholes. I do not expect them to be dry if totally immersed for any significant period of time. YMMV

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Smart to test your gear. I usually just give mine a squeeze to make sure air doesn’t leak out but your method sounds better. Double-bagging seems wise too.

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A trick we used in the USMC in wet operations. In both extended field operations and amphibious operations:

Use a garbage bag. They come many different sizes so get the size you’ll need for the job.

Fill it no more then about 40% and pic it up to spin it, so you make a “neck” to close it over the gear and expel all the air you can… Now, invert the remaining bag over the bottom part you just made and spin it again, expelling air and then tape it off. Place that whole package into a water-proof bag (dry bag). Take the water proof tape with you and also the box of garbage bags, so if you damage them in use you simply replace them as you go. I have done this in operations that lasted many weeks and also in Amphib/Recon training, where insert and extract were all buy rubber boats and the in some cases we did “lock-outs” from submarines, coming up from 35 to 40 feet below the surface. Never have had any leaks at all using that system, and it’s super cheap and very effective.
The dry bag is the outer layer so it’s tough and resistant to wear and punctures, but the inner garbage bags are the layers that actually makes the contents water-proof


I just had 2 SealLine Baja bags delivered yesterday. A 20L and 30L to add to the 10L and 20L I already had. All are the rubber texture you mentioned. I think i will test them all and see what happens.

Yes! And you can accomplish the same with a thinner material, Nyloflume. That’s what I use as a pack liner for my DCF backpack, using the technique you describe.

My “test” is obviously taking it to an extreme for the nylon bags, since I don’t think they contemplated prolonged submersion; probably not for the Baja bags either, it’s just that that material is impermeable except for the seams and the closure.

What I learned is that I’d definitely use a liner in those nylon bags and probably the vinyl ones, too for things that absolutely cannot get wet.

If you closed the bags during a time of relatively high humidity and then placed them in cold water you can expect to see condensation inside.

I usually double bag stuff that I really need to stay dry - keys, cloths, sleeping bag.

One more trick I use is to buy freezer boxes and freezer bags made for food. It’s only for the smaller things obviously, but if you place your small things in the bag and press them closed (or zip them if that’s the kind you buy) and then put the bag inside a freezer/food box, you are virtually guaranteed to have those items stay dry. Cell phones, cameras, wallet, extra batteries, medications, food items, Fire starters, and things made from paper and many other things that can’t get wet. Easy, Cheap and very reliable.

Kayaking or diving?

Kayaking or anything on or near the surface. The food boxes won’t stand a lot of pressure so you can’t take them deep.

It seems pretty ridiculous to make dry bags from eVent or sil-nylon in the first place. The main point of a dry bag is that they must be DRY, so why use a semi-breathable fabric that’s less waterproof than less expensive, non-breathable alternatives that are proven to work and be durable? Saving a few ounces is meaningless if your critical gear gets wet, and you pay a premium price for less protection. Where’s the value in that?

I suggest that you re-do your testing with a different methodology:

  1. Fill the bags with air and close the tops. Do not put anything else in them.
  2. Submerge the bags fully and squeeze them.
  3. Look for bubbles and mark the locations of any leaks.
  4. Seal them with Aqua seal, Goop, Lexel or whatever non-silicone sealer you have on-hand.

Not only will you be able to fix your bags, but you’ll also learn how waterproof the roll-top seals are.