“Backpack pumps are uncomfortable. They leak. They only last a couple of years of hard use. Everyone dreads using them. Water is heavy and awkward to carry. But piss pumps are an essential wildland tool. Deal with it.”

These are common assumptions about legacy backpack pumps (leaving out the obscenities). When Tied-In Equipment started prototyping the Double Lunch, we questioned all of them to get down to the most basic, fundamental principles and work from there. By fundamental principles, we mean human physiology and the laws of physics. To show that thought process, let’s pick apart just the first part of that first sentence:

“Backpack pumps are uncomfortable…”

What about these pumps is uncomfortable? Well 5 gallons of water weighs about 41.6 lbs, that’s heavy enough. Plus the average firefighter is already wearing 35-45 lbs in their line gear. Carrying 80 lbs on your back in rugged terrain is fatiguing if it’s well-distributed and stabilized perfectly. But the bladder of an old school backpack pump is poorly anchored and unstable, and the effort required to resist the inertia of water movement results in additional fatigue.

Why is the load unstable? It sits high on top of the line gear yielding a poor center of gravity. The old school version requires wearing backpack straps on top of the backpack pack straps of firefighter line gear and this results in compounded load carriage.

What’s load carriage? That’s the use of load-bearing personal protective equipment worn primarily over the thoracic spine (chest)—backpacks are a prime example. Load carriage restricts the movements of breathing and calls for accessory muscle group involvement to facilitate breathing during exercise, thus increasing exertion, physical effort and the speed to fatigue. This load carriage-induced respiratory muscle fatigue increases the energy cost of breathing, using up valuable oxygenated blood that your legs sure would appreciate. Knowing this, it doesn’t take a rocket surgeon to tell you: two sets of back pack straps and lots of unstable weight up high result in one tuckered taco climbing that hill.

So how can backpack pump design mitigate load carriage? Alright let’s get rid of the backpack straps. Instead, anchor the load to the firefighter’s well-designed line gear which distributes weight evenly around the hips… pause here for fat joke… and has already taken into account the dynamics of load carriage. While we’re at it let’s contour the shape of the bladder to hug the shape of the line gear. That’ll further stabilize the load, drop the center of gravity, and even result in some baffling of water movement inside the bladder. These changes (better anchoring, lowering the center of gravity, contoured design) alleviate significant sources of firefighter fatigue. Now we’re working with physics instead of fighting it. These changes might even make for a piss pump that’s… enjoyable to use?? (Hey! Did you just gag a little?)

But hold up, water is still effin’ heavy! Yes, Newton. That’s a gravity problem. Can’t change gravity… but we can make a 2.5 gallon pack that’s half the weight. Enter Pocket Snack. Ain’t nothin’ wrong with that.

There’s our spin on First Principles thinking.

It’s how Tied-In resolves design challenges with high impact solutions. And we’re just getting started…