Reasons why packs aren't water repellent? - Backpacking Light (2024)

Nov 11, 2015 at 12:08 pm#1334110

These last few years have been kind to me rain wise here in So. California but now we are expecting El Niño to kick in this year and change all that. This got me wondering why pack manufactures don't put a water repellent on their packs? I use a trash compactor bag on the inside of the pack for weather and have a pack built from dyneema and in places 100% spectra which doesn't absorb water but, it does hold water in the weave which adds weight fairly quickly. Before adding a water repellent to the pack that would address this problem, would I be exchanging one problem for other problems by doing this?

Nov 11, 2015 at 12:46 pm#2237477

does it keep water out of the inside of the pack? must not if you're using a trash compactor bag that's my question, why aren't packs waterproof?

The reason packs aren't maid of waterproof material lies in how much true waterproof material would weight compared to the fabrics commonly used in pack construction along with the weight of a typical pack cover. Cuben fiber packs might be an exception, but you are trading a lot of durability. As to using water repellent treatments, treatments are going to add some weight, and I would question just how well they'd work. For the occasional shower/thunderstorm, probably would work, but for several days of rain? I have serious doubts. But I haven't actually talked with someone who has done it. I stopped lining my pack with a trash bag after I realized that I stored everything in those uberlight zpack cuben fiber stuff sacks which are already decently waterproof. Though I still carry the 1.5oz cuben fiber pack cover if I'm expecting days of rain (keeps the contents in the mesh pockets dry and when I'm dealing with a lot of rain, there tends to be more stuff stored outside the pack).

For many years I always thought backpacks should NOT be water proof; thought they should 'breathe' so that any damp gear inside might dry a bit. (and this might be best in a dry desert climate or the Sierra)… When they started showing up with packs made with wp coatings it still seemed foolish as the seams were not sealed and would leak anyway. Also, even if packs are made with wp fabric and seam sealed it will not stay wp for long… abrasion and dirt contamination will cause them to leak… just like our wp jackets. So… I've always just used a rain cover on the outside and wp stuff sacks for critical gear inside like my down bag and jacket. Rain covers and stuff sacks are easier and cheaper to replace and/or make waterproof again that a pack. billy

The reason for the trash compactor bag is two fold, it's mostly used to separate the wet equipment (tarp for one) from the things that need to stay dry (sleep system & clothes not worn). The pack doesn't leak water during a rain but it could fill with enough water to ruin a day if there is a slip during a water crossing during wet weather with no chance to dry out.

I've been thankful for the trash compactor bag….even though I can only remember two times in five years when my platy bladder leaked (operator error), it made a difference in keeping my sleeping bag and clothes dry.

The area of fabric required to make a pack is so small, the extra weight of making it waterproof is negligible. Less than 1.5 yd2 of fabric is required. Maybe it would add 1 ounce for a thick waterproofing. The only thing I put in my pack that is very wet, is my tent, but I put it in a waterproof bag. Sometimes I strap it on top, outside the pack. My back sometimes get sweaty. You don't put a pack cover between back and pack, so the pack needs to be waterproof. I don't like having an extra object – bag liner or cover. It just seems like a kludge to make up for deficient fabric. I think most people are happy with this though… Breathable fabric works for a jacket or boots or whatever, because your body is warmer than the outside, so water is "driven" out of the fabric. With stuff in a pack, it's about the same temperature as the outside so there's much less flow of water vapor. I just happened to have some 200D waterproof PU fabric that I made a pack with, but it leaks a little in the rain. I coated it with seam grip diluted with Tolulene, but it still leaks. I coated it again with more seam grip and less tolulene – waiting for a rainy trip to test this. I wonder if Dyneema fabric would be more waterproof, sounds like it would be. That's probably what I'll use next time, although the 200D nylon is plenty strong enough. I think higher D fabric, with thicker threads, is less waterproof, because the gaps between threads is also larger so harder to get a good waterproof coating?

It is not hard or expensive or heavy to use WP fabric for your pack. I use X-Pac fabric and it is WP. That stuff is good. Where it gets difficult is at the seams. The sewing always leaks unless you take quite complex measures. Remember that the seams are usually under some sort of tension, which makes sealing them harder. In addition, many packs have lots of seams on the panel against your back – even harder. The industry standard 'solution' to this is to bind the seams with some non-WP tape. That is more for covering the cut edges than making the seams WP though. And it does not work. A very good solution in practice is a WP poncho over you and your pack. That blocks the cascade of water running down between your back and the pack, which really helps. WP jackets are of course useless here. Despite that it IS possible to make a WP pack. But it takes effort and time, which translate to $$ for the customer. My MYOG packs ARE waterproof. Cheers

Water repellent, yes and most are. Waterproof with compromises, yes. Most pack cloths have some DWR and water will bead up and roll off. As Roger said, they will leak at the seams. And all the nice cushy 3D foam is a sponge. WaterPROOF packs are generally heavy and have lousy suspensions and hydration options are dismal as well. . Most are made for short distance use like portaging and canyoneering. Outdoor Research and Exped make some light waterproof packs, but the thin fabric is fragile and the suspensions are on the stuff-sack-with-shoulder-straps level. They are okay for summit/day hikes, but I haven't seen a waterproof pack that makes me want to wear it for multi-day trips in lousy weather. For hiking, one of the main failing of a waterPROOF pack is where to put your wet gear. Assuming you want a waterproof pack to deal with wet weather, you will soon collect a wad of wet tarp, muddy ground cloth, rain gear and clothing. With a waterproof pack, you end up stowing all the wet stuff in with the dry stuff. My backpack is my trail office, with the pockets to organize and keep my gear close at hand. With most waterproof packs, you're lucky if you get one outside pocket and the rest is a big monolithic block that you have to remove and open the roll top to get to anything while underway. This is where a trash compactor bag or an effective dry bag inside your conventional pack works, keeping the dry stuff separate from the wet stuff. It also keeps the dry stuff dry when you open your pack in the rain. As Roger said, a poncho will keep ALL your pack dry, including the suspension. One of the joys of hiking is to have the deluge stop, taking off your rain gear, and then putting on a wet pack with a soaked suspension. It's on a level with putting on cold wet shoes in the morning. NOT.

Many/most pack fabrics are treated with a DWR, dirt and abrasion just kill it off pretty quick. A double coated fabric would stop water from absorbing into the exterior, but that adds extra cost, exposes the outer coating to abrasion, and for reasons I don't understand double coated fabrics apparently have less tear strength than single coated fabrics.

I'm wondering if anyone here lives or backpacks in an environment that truly needs a completely waterproof pack or backpacks in the rain for any huge amount of time where having one would be an advantage. Even on long trails I've managed to get to a hotel or shelter or dry everything out in the sun that needs it. As mentioned above anything along those lines is basically a river runners dry bag. In the 1970's I did a lot of backpacking on the Continental Divide during the monsoon summer seasons, my clothes would just rot off, but even with my old Kelty pack I was able to keep my sleeping bag and long johns dry. I used ponchos, one wool one and one army, worked fine.

Thank you all for your responses and from them, I'm going to coat the outside of my pack with a completely natural coating which is water repellent and will also reduce friction to the fabric weave, which in turn, will keep the water from sitting on the fabric. After testing it out, I'll post my thoughts of how effective it is.

"In addition, many packs have lots of seams on the panel against your back – even harder." I just have one seam vertical and one seam at the bottom. Flat felled seams. Plus 3D mesh and straps at the rear. Seam Grip seals them completely, also strengthens the seams, not that that's important. Next time I'll use X-Pac. I'm rooting for my pack to wear out, but I think I may wear out first : )

I used an X-Pac MYOG backpack to thru-hike the CT this summer. Just to be uber-safe, I seam-sealed it. Due to bad luck, my pack ended up sitting outside on a rock for about 30 minutes in a raging deluge of an apocalyptic thunderstorm. When I got to shelter, everything was bone dry. I wouldn't expect it to stay dry if submerged in a lake/stream, but even in torrential rain, the X-Pac was bomber!

I think submerged in stream is too big a threshold. If you were kayaking or something then this would be important. Otherwise, this would be too heavy. Apocalyptic thunderstorm is a reasonable threshold. Living in the PNW, I occasionally encounter rainy periods, although I look at weather reports and try to choose times or locations that aren't so bad.

Nov 12, 2015 at 12:52 am#2237626

Terry, Please note the distinction between water proof(high resistance to water penetration), and water repellent, often called DWR. Most pack fabrics have DWR on the outside when new, and they can be refreshed with sprays. My favorite is Tectron Wet Guard, because while not as good as it was, is still very effective, and contains no silicone or other contaminants that will disable the water resistance in GTX and other waterproof breathable membranes (WPBs). Most pack fabrics also have some kind of water RESISTANT coating on the inside, but that wears away eventually also. And as Roger notes, seams can also leak. Maintaining good DWR will help to keep water from saturating the outside of the pack fabric, especially if it is nylon, which readily absorbs water. But only a good water resistant coating on the inside will prevent water from penetrating in a deluge or extended rain, and most packs do not have that. Unfortunately some of the more rugged fabrics, like dyneema or spectra reinforced nylon, in my experience do not have very good water proof coatings. I don't like the Dimension-Polyant fabrics like X-Pac, because while waterproof, they don't have the self-sealing qualities of nylon at the needle holes in the seams, and some of the lighter versions are not at all waterproof. I like Cuben laminates even less for similar reasons, not to mention poor abrasion resistance. So for a pack I am making, I'm using a very rugged nylon tent floor material from Australia. It is only 100 denier, but with a tough waterproof coat, comes up to 3.4 oz per square yard. I will carefully seal the seams with Seam Grip. I think it will be waterproof, but will also make new stuff bags from highly waterproof but lighter fabric, much lighter than pack fabric that must withstand abrasion. For buying packs, I would look for a distinct waterproof coat on the material, and if it is a polyurethane coat, refresh it with McNett TentSure when it starts to wear. Maybe pack covers were suitable in Colin Fletcher's day, but these days I think having to use garbage bags and other sundries on packs is shameful given the technology currently available.

Take any well used pack and look inside the pack while holding it up the light. The bottom of the pack will have tons of holes in it from setting it down on the ground. You might not see the holes looking at it from the outside. Most people keep their sleeping bag in the bottom of the pack, right where the majority of pinholes develop. How durable of a pack fabric do you need to prevent this? I can see waterproof fabric being useful if the weight penalty isn't much. I like the idea of throwing a fleece in the top of my pack, outside of the trash compactor bag, and having it stay dry in the rain. I also like the idea of the stuff that I keep outside of my liner not getting wet, especially in cold weather when I have to handle it with numb hands. Like I would really prefer my bear bag line and cooking pot not to be wet when it's near freezing. But I'm still going to put my down stuff in a liner.

…if you buy them that way. I've slowly transitioned all my packs to Cuben Hybrid primarily for this reason.

> I'm wondering if anyone here lives or backpacks in an environment that truly needs a > completely waterproof pack or backpacks in the rain for any huge amount of time where > having one would be an advantage. Yeah, plenty of times. Maybe the longest was 4 weeks of rain in France one time. That destroyed Sue's shoes – at least the leather parts. When they dried out – the leather shrank very badly. Foot mangling. But my X-Pac fabric pack survived very well under a silnylon poncho. It happens. Cheers

I've found XPAC to a reasonably good job. I flipped a kayak with a X42 Roll top bag attached, and the kayak went a couple hundred yards in class 3/4 water and there was minimal water in the bag, no more than the dry bag attached to the rear of the kayak. This was with no seam sealing. For general rainy weather, slush and snow, I find it to an acceptable job. Sure a tiny bit of water can get in, but it is vastly different than experiences with packs which gained a 1 lb of water weight and most stuff was soaked inside. IMO, a rain cover is not a very effective solution. Sure, they are good if you are upright and have the cover on, but a lot of the times for me, I avoid putting the rain cover on ..or you do something like leave your pack outside your tent and it starts to rain .. No solution is perfect, but I have found XPAC / roll top pack bags to do a good enough job to be essentially a non issue.

"Maybe pack covers were suitable in Colin Fletcher's day, but these days I think having to use garbage bags and other sundries on packs is shameful given the technology currently available." yeah!!!! But if covers or liners work for you, great : ) Pinholes on bottom aren't a problem unless you're submerging, like kayaking. Water runs downhill. It's holes on top that are the problem – rain gets in and runs down into stuff in your pack. And the fabric on top is a horizontal surface so easier for water to get in. On the sides, water is more likely to just run off. Once I had a platypus zip top open and all the contents came out in pack. I was testing so it didn't matter. I won't put a water bag in my pack again. Re-used soda bottles are pretty reliable. Rarely, I forget to tighten the cap, and some water leaks.

"I'm wondering if anyone here lives or backpacks in an environment that truly needs a completely waterproof pack or backpacks in the rain for any huge amount of time where having one would be an advantage." I've done a small amount of caving, and having a true waterproof pack would have been nice for what I did, and if I did more trips I'd probably spend the money to get one of the caving-specific packs that exist out there. Way more abrasion than normal packs are designed to take, and partial or complete submersion was fairly common. Obviously a very niche case though.

I prefer uncoated, non-waterproof fabric for my packs. I make my own so I have my choice of fabric. My current favorite is 1.9 ounce uncoated ripstop. Anything that must stay dry goes inside plastic bags. These items would easily stay dry in a full emersion accident. When it rains I let the rain run through the pack (and around the plastic wrapped nuggets). No pack cover. No problem. The porous pack cloth dries quickly when the rain stops and water doesn't pool anywhere in the pack because it isn't waterproof. And the big bonus for a heavy sweater like myself is that I can remove the pack bag after each trip and run it through the washing machine. The washing gets rid of sweat, salt and stink.

"Pinholes on bottom aren't a problem unless you're submerging, like kayaking. Water runs downhill. " I keep my sleeping bag in the bottom of my pack and I've gotten the bag wet by setting it on the wet ground.

Since I got my first HMG pack I'm going to find it hard to go back to a nonwaterprooof pack. No worrying about a pack liner or cover. It always annoyed me having to put another bag inside a bag because the outside one wasn't waterproof. I did have good luck with my older macpac canvas pack, it seemed storm proof despite no sealing, stuff inside my never got wet. Downside is I'm pretty sure it would have gotten heavier from saturated face fabric. I notice MHW is selling packs with a weatherproof lining of some sort. Good to see such features becoming mainstream.