Who wants credit for this one?

[CaptainSuburbia]

Didn't Roach once say "never pass up a chance to pee" or something like that?

[JtheChemE]

I'm an engineer too, it passes all the sniff tests to me.

So can you explain to me why it makes sense to you? (I assume you're a chemical engineer?)

It's hard to imagine a perfect hike where water input matches water output, so that is the key assumption. Water input = drinking, water output = respiration, perspirations, urination (perhaps some other mechanisms I am not aware of).

So if we do a basic material balance, you are likely to output more liquid than input. So with that in mind, retaining waste liquid is excess matter to keep warm. In a perfect world if you input the exact net output, than indeed it wouldn't make too much of a difference from mass balance perspective (energy balance also really complex, so maybe assume water input is approximately body temp). While the body is a complex system, if you consider just water the back of the envelope energy balance checks out.

You can take this into the weeds ad infinitum, so I have nothing else to say. Too many potentially good topics devolve into an exercise in pissing contests, and I'm not into that. The moral of the story is simple, don't plan your day around peeing (as Polar implied I suggested, which I did not) but don't hold your urine to save 30 seconds on the day.

[CaptCO]

My freediving instructor always told me if I'm not pissing in my wetsuit, I'm dehydrated. Warms you up for a few minutes while diaphragmatic breathing

[Aphelion]

I'm an engineer too, it passes all the sniff tests to me. What's the specific heat of water again? ...

The urine within a bladder isn't attempting to reach thermal equilibrium with the outside air, it's at equilibrium with your body temperature. It takes the same amount of "wasted" energy to keep urine warm as an equivalent volume of blood (probably less so, since urine hopefully isn't circulating out to your colder extremities). Functionally, emptying the bladder is just reducing body mass while maintaining metabolic/thermal generation. If we assume an average american person of around 84 kilos, and an average bladder capacity of around 500mL, that's a loss of ~0.6%. Becoming 0.6% smaller will technically help warm you more, but I doubt anyone would notice it sans placebo effect.

[polar]

Not trying to turn this into a pissing match, just trying to debunk a piece of cold weather advice that has persisted throughout the years. Because if the advice isn't really valid, then there's no reason to keep it.

Urine is the output of metabolism. When it's produced, it's already at body temperature. It is then kept in the bladder, which is well insulated by the body. There are no major mechanisms of heat loss at work in the bladder (conduction, convection, radiation, and evaporation). So besides the normal energy used for the metabolic process, you don't need a huge amount of energy to keep it at body temperature.

The input of the metabolic process is more important in this case. If you drink cold liquid, then your body would need to use energy to warm it up to body temperature. But if your drink is already at body temperature or warmer, then no extra energy is wasted.

[AndrewLyonsGeibel]

Just don’t pee into the wind. Other than that. Meh.

[Bale]

Just don’t pee into the wind. Other than that. Meh.

And don’t eat yellow snow.

[CaptCO]

Just don’t pee into the wind. Other than that. Meh.

And don’t eat yellow snow.

Wait.. you’re telling me the sweet taste isn’t from tree sap? Uh oh

[Conor]

Not trying to turn this into a pissing match, just trying to debunk a piece of cold weather advice that has persisted throughout the years. Because if the advice isn't really valid, then there's no reason to keep it.

Urine is the output of metabolism. When it's produced, it's already at body temperature. It is then kept in the bladder, which is well insulated by the body. There are no major mechanisms of heat loss at work in the bladder (conduction, convection, radiation, and evaporation). So besides the normal energy used for the metabolic process, you don't need a huge amount of energy to keep it at body temperature.

The input of the metabolic process is more important in this case. If you drink cold liquid, then your body would need to use energy to warm it up to body temperature. But if your drink is already at body temperature or warmer, then no extra energy is wasted.

I prefer to write "engineerz drool" in the snow with my pee. I'm usually short on "ink" if you catch my drift.

I pee and sweat a ton. I try to keep my urine from changing to a bright yellow, sometimes it's possible, sometimes not. But, when when the urge hits I'll square the ol shoulders down wind and start spelling "eng". I can understand why women are at a disadvantage for the pee relief, especially when it's above treeline and the wind is whipping. But, i go in excess of once per hour while I'm out. Not sure if it is helping or hurting whst for my body is negligent hest loss, i have plenty to go around....

[AndrewLyonsGeibel]

Just don’t pee into the wind. Other than that. Meh.

And don’t eat yellow snow.

Wait.. you’re telling me the sweet taste isn’t from tree sap? Uh oh

That means you’re eating diabetic pee.

[highpilgrim]

That means you’re eating diabetic pee.

Probably better than asparagus piss.

[Bale]

That means you’re eating diabetic pee.

Probably better than asparagus piss.

Ha, you beat me to asparagus! That’s potent pee, can you imagine the smell of pissing into a bottle at 17k after eating that stuff?!