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Water Needed for Hiking: How Much Should You Bring?

How much water for day hiking

It’s important to bring water with you when you go day hiking to replace the fluid you lose to perspiration, help keep you more alert, and flush waste products out of your body.  Not bringing enough water can lead to discomfort, while bringing too much can slow you down. How much water do you need and what’s the best way to carry it?

1 Liter every two hours

If you’re actively hiking, it’s good to drink about 1 liter (32 ounces) of water every two hours. That’s a good rule of thumb based on my experience hiking year-round and in a wide range of climates. You might need more or less depending on the temperature, humidity and body weight, but that’s a good estimate of what you’ll need to carry if you can’t refill on your route.

Water bottles are best carried where they are easily accessible on the outside of a backpack rather than being buried inside it. Backpacks with stretch side pockets are convenient, so you can reach back and grab a bottle to sip from while walking. Can’t drink and walk at the same time? Stop for a few minutes every hour and sip from a water bottle while you take a five-minute break.

How do you know how much water to bring?

If you have a guidebook, it should give you a time estimate for your hiking route. If you just have a map, calculate the total distance of your hike. Divide that number by your pace in miles per hour. This will usually be somewhere between 2 or 3 mph. For example, I can hike 3 miles per hour on a flat trail. If the distance of my route was 9 miles, I’d want to bring 1.5 liters. It’s just an estimate of what I need, but fairly accurate.

Does it have to be water?

No. You can drink any non-alcoholic fluid. Water is usually cheap and easily available, but you can also drink tea or juice if you prefer, or add an electrolyte mix to your water to make it taste better.

What about hydration packs?

If you have a hydration pack or a backpack with a hydration reservoir pocket, being able to sip on a hose while you walk is very convenient for day hiking. It’s great because there’s such a low barrier to drinking and having a hose connected to your shoulder strap is constant reminder to take a sip. Buying a 3 liter hydration pack is a good size for a long day hike. If you don’t need all 3 liters, don’t fill it up fully.

How do you know how much water is left in your hydration pack?

That’s one of the problems with hydration packs. You don’t know how much water is left in the hydration bladder when it’s hidden inside your backpack. That’s why some people prefer drinking out of transparent bottles. Hydration packs are super convenient though and you can just open your pack and check to see how much water you have left if you want to know.

Can you drink too much?

You can but your body is pretty good at flushing extra fluids out by making you pee. Peeing on a hike is normal and you shouldn’t be ashamed to ask your friends to let you take a bio break on a hike. The color of your pee is also a good indicator of your hydration level. If your pee is bright yellow or even brownish, you need to drink more water. If you make a habit of drinking when you’re thirsty and eating a salty snack once in a while to replenish your electrolytes, you should be fine.

Can you refill water bottles or a hydration pack on a hike?

Absolutely. If you want to refill using a natural water source like a stream or lake, it’s best to filter or purify your water using a simple product like the Katadyn BeFree or Sawyer Squeeze that lets you pour your filtered water into your bottles or hydration bladder. A Grayl Geopress is even easier because you can drink from its water bottle directly.

Being able to refill using natural sources on a hike will let you increase the distance you can hike, improve your self-reliance, and hiking skills. How can you tell where streams or ponds will be along your route? It’ll be marked on your map.

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  1. It can be tricky in the winter too, as the hoses may freeze for hydration packs, rendering them useless, even if they are marked as ‘insulated.’ Something with some sugar content like a Gatorade can be helpful as it will take a little longer to freeze in my experience. Keeping a Nalgene type bottle can be helpful too. Keeping the bottle upside down keeps the water from freezing over the drinking part of the bottle, and when extra cold, having the water bottle inside your jacket (and sleeping bag if going overnight) can prevent your water from freezing too. Tricky business!

    Ps… Love the site Phil. It’s helped me a bunch over the years and I’m proud to say I finished my 48 in December, with plenty of winter hiking to boot!

  2. Solid advice. I would emphasize that being fully hydrated by drinking your share of fluid before exertion is always recommended. For reference 1 litre weighs about 2.2 pounds so on a day hike no big deal to carry 3 litres from home and not have to worry about filtration or tablets. When carrying a pack on multi-day trips the extra weight is noticeable. If unsure, i carry an extra litre similar to pilots in times of war-only to be used in an emergency.

  3. Jean Marc Lapierre

    During winter, I keep the hose inside my jacket instead of leaving it attached to my shoulder strap. After I finish drinking, I blow back the water from the hose into the bladder so it does not freeze. I have been doing that for many years and have not had freezing water problem. It helps to fill the bladder with lukewarm water to start the day.

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