You're also probably spending half the day pissing it all out as well. You absolutely do not need 8 liters of water for anything I just described.
Maybe you just hike differently to what I assumed.
I do the occasional hike anywhere from 4-8 miles and I usually drink an extra 1-2L for the day - that's how I reckon I'd double my intake for a 12-15 mile hike. I don't piss like a race horse, the hikes are in 95-105 degree weather, and I go at pace. To each their own.
https://www.goarmy.com/soldier-life/fitness-and-nutrition/co...
Military suggests roughly 4 liters for an active person, for an entire day. Even adding another liter for strenuous and in dry climates, that's far less than 8 liters.
If you're awake for around 16 hours, not sure why drinking an average of 500ml of fluids every 2 hours seems excessive to you. Or why drinking 1L of fluids every 2 hours (when your agenda for the day includes doing a 15 mile hike in hot weather) is considered a lot.
If what I've described above would make you go to the bathroom every 30 mins, perhaps see a doctor.
I appreciate the feedback, but perhaps don't tell me what to do.
I don't think most adults should need more than 3 liters of water for a day long hike if they are already properly hydrated. The idea is to hydrate for 24 hours before you exercise. Then during the exercise, you take small sips occasionally. After an hour, you may need to begin replacing lost electrolytes. You also want to drink more often at high elevation and in the cold.
You can actually check how much water you'll need during exercise. Weigh yourself, exercise for an hour, and weigh again. The lost weight is the water you lost and need to replenish.
In any case, you should be peeing every 2 to 4 hours. If the water is clear, you're hydrated. If the water is dark yellow, you're really not hydrated.