Gear Review: Sea to Summit Flow 35L Dry Pack

January 16, 2015  |  In Gear Reviews   |   Tagged , , , , , , , , ,   |   7 Comments
Sea to Summit Flow 35L Dry Pack

Sea to Summit Flow 35L Dry Pack

Waterproof Backpack
Sea to Summit Flow 35L Dry Pack
$200, 35L/2,136 c.i., 2 lbs. 4 oz.
One size

We reached the first, deep pool of water that we had to swim across in the narrow canyon called The Subway, in the backcountry of Utah’s Zion National Park. I tucked my expensive camera gear inside my new Sea to Summit Flow 35L Dry Pack, with my food and extra clothing—and hoped this pack would prove true to the company’s claim of being infallibly watertight. (I did put my camera gear inside another dry bag first, of course.) Then I dropped into the frigid pool—wearing a dry suit—and kicked across it, floating the Flow. And yes, it did keep its contents completely dry—thankfully. But more than just a glorified dry bag with shoulder straps, it proved itself to be a solid and comfortable pack for hiking all day, too.

I carried the Flow 35L with 15 to 20 pounds inside—including, at times, a full dry suit in a stuff sack—on a one-day hike and descent of the Subway in Zion, which took us just under seven hours car to car and involved three swims across pools, a lot of walking in water, and about six miles of hiking the trail above and below the Subway. The perforated foam shoulder straps and hipbelt were comfortable with that much weight, and drain water and ventilate well, and the hipbelt is removable to shed a few ounces of weight.

Flow 35L Dry Pack harness.

Flow 35L Dry Pack harness.

A top-loader with a roll-top closure for the main compartment, the Flow 35L is made with TPU-laminated, 420-denier nylon and is fully seam sealed. Water never penetrated the pack’s main compartment when I floated it across deep pools. You have to nearly fill the pack to create enough tension on the roll-top closure to ensure a watertight seal, but side compression straps help make a slightly undersize load watertight.

This pack is bulletproof—I slammed it into canyon walls and dropped it repeatedly onto rough sandstone, and it’s no worse for the wear. But the stretch mesh side pockets, big enough for a liter bottle, are its only vulnerable part. The upper compression strap on each side has two positions of attachment, to accommodate attaching objects of different sizes; I fit a fairly large tripod under the straps.

I didn’t quite fill the Flow 35L for the Subway, but 35 liters is a good size for technical canyon descents of a full day or even two days if you pack light, when you may be carrying a longer rope and more gear than we needed for the Subway. A white interior makes it easier to see contents. I like the big, top handle for lifting and lowering the pack through tight spaces even while wearing neoprene gloves.

Sea to Summit Flow 35L Dry Pack.

Sea to Summit Flow 35L Dry Pack.

Organization is basic, as expected in a dry pack (to minimize potential points of leakage). There’s a zippered, internal, stretch pocket for small items like keys and phone. A two-liter front pocket has a waterproof zipper with a rain hood; it keeps out rain and water if briefly immersed, but is not completely waterproof in a sustained immersion. There’s also an externally accessed, zippered pocket for a water bladder, so you can refill it without having to open the main compartment and potentially exposing its contents to water.

Sea to Summit Flow 35L Dry Pack.

Sea to Summit Flow 35L Dry Pack.

For canyon hikes when you’re in water, river trips when you want a dry pack that offers real support for 15+ pounds for side hikes, or any hikes in consistently wet environments, the Flow 35L Dry Pack is a durable choice.

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NOTE: I’ve been testing gear for Backpacker Magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See all of my reviews by clicking on the Gear Reviews category at left or in the main menu.

—Michael Lanza

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7 Responses to Gear Review: Sea to Summit Flow 35L Dry Pack

  1. Dan   |  February 7, 2017 at 12:11 pm

    Hey Michael, thanks for the great review! I know this is an old post, but I’ve been eyeballing this pack and yours is one of the few reviews on it. Do you have any experience using this as a carry-on bag for flights? I saw an estimate of the dimensions that are just over the maximums but was curious if you had any experience.


    • MichaelALanza   |  February 7, 2017 at 12:17 pm

      Hi Dan, good question. I have not used it as a carry-on, but I’ve certainly used packs in the 30-35L size range as carry-ons without a problem. The Flow 35L isn’t rigid, and while I can’t say for certain, I think you’d be able to use it as a carry-on and fit it in the overhead bins on most commercial flights.

      • Dan   |  February 7, 2017 at 11:08 pm

        Hey Michael,

        Thanks for the quick reply! That’s what I suspected. I’ve seen some rigid carry-ons that have no business in an overhead…

        One other follow up: It sounds like you’ve used it a fair amount hiking. I’m not sure how much if at all the design has changed but the back padding doesn’t appear to be designed with much air flow in mind. How was the back ventilation? Did it seem to just get hot and swampy on your back or ventilate ok? I know it won’t be the same as a suspended mesh frame but I tend to hike pretty hot.

      • Dan   |  February 8, 2017 at 9:13 am

        Hi Michael,

        Thank you for the quick reply! That’s about what I thought as well. Hopefully we’re both right! I had a quick follow up question as well: How well does the back support foam ventilate? I’ve had some packs where once you start moving it is miserably hot and swampy on your back. I know this isn’t a suspended mesh design but with your hiking experience is it comfortable? I tend to hike hot and the solid looking back panel makes me a bit nervous.

        P.S., sorry if this is a double post, thought I commented before but don’t see it up.

        • MichaelALanza   |  February 8, 2017 at 9:22 am

          Hi Dan, you raise a good question. As you can probably see from the photo of the back panel, it’s not really designed for air flow; it’s designed for closely hug the torso. Considering that this pack is intended for use in water–often cold water, when the challenge is staying warm rather than staying cool–that design makes sense because it also helps the pack carry more stably and comfortably.

  2. Jon Frisby   |  June 13, 2015 at 1:35 pm

    Hi Michael – nice review. How do you think this would be as a technical climbing pack?

    • MichaelALanza   |  June 15, 2015 at 7:53 am

      Thanks Jon. I didn’t test this pack with the amount of weight I’d carry in a climbing pack–25 to 35 pounds–and I’m not sure how comfortably it would handle that much weight. While it has the durability of a climbing pack, it does not have the features I’d normally look for in a climbing pack, like external tool attachments, a rope strap under the lid, and durable external loops for lowering the pack. For $200, you can find a pack that’s designed for climbing.

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