Should I Carry Water For a Half Marathon?

Either you’re just starting out in your half marathon training or you’ve reached a long run exceeding the needed amount of water one bottle will carry. Eventually, you’ll need to answer the question, “should I carry water for a half marathon?”

Should I carry water for a half marathon?

Carrying your own water during a race provides many benefits over the alternatives of not carrying your own water. During your training, you should know which method to carry the water by, how much water you’ll need, and approximately how much water you’ll sweat out during the race. If you don’t carry your own water you’re stuck with the water aid stations or if you’re lucky enough, friends that you’ve staged along the racecourse with water waiting for you.

If you’re going to carry water on the racecourse be aware of these things:

  1. You’re adding more weight – If you decide to wear a hydration pack for your half marathon race and you fill it with 2 liters of water you’re adding about 4.5 to 5 pounds of weight (2.5 kilograms, depending on the weight of the hydration pack). While this is not a significant amount of weight it still adds up. The pack will become lighter with each mile you pass and water you drink.
  2. Carrying a normal water bottle – you’ll have to hold on to it the entire race. Nothing drives me crazier than to hold something in my hand when I run. It literally drives me bonkers! However, there are many racers who use custom formed water bottles that adhere to your hand better than a normal water bottle and they have no problem. One benefit of a water bottle is that you can refill it at the aid stations a lot easier than a hydration pack. Although you shouldn’t have to fill up a hydration pack during a half marathon race.

Full Disclosure: This post includes affiliate links for which, LERK Publishing, LLC., may make a small commission at no extra cost to you should you make a purchase.

Benefits of bringing your own water to a half marathon race

  • you’ll know how much water that you brought and approximately how much water you’re going to drink
  • You can space out your drinking more evenly, for example, drinking 4 gulps of water every mile or some variation.
  • You can take your energy gels at your leisure and not determined by the water aid station layout.

Drawbacks of bringing your own water to a half marathon race

It’s hard to know how much water you’re actually drinking at a given time. You can regulate this a little if you determine how much water one of your gulps is either from a hydration pack and/or a water bottle. This really overdoing, but hey, if you sleep better at night because one of your gulps is exactly one fluid ounce of water – go for it!

Benefits of using the on-course water

So if you decide to roll the dice and use the on-course water you won’t have to worry about these issues:

  • You’re not carrying any extra weight. Less weight will allow you to run faster and possibly get that PR (Personal Record) you’ve always dreamed about.

Drawbacks of using the on-course water

  • You’re at the mercy of the racecourse to determine when you can take energy gels – If you’re taking energy gels during your race, you’ll need to take them at the water/aid station. Energy gels need to be taken with water so that your body can properly oxidate the energy gel and turn it into energy faster.
  • All cups of fluid (water) are not equal – Every cup of water will have a different amount of water in it. Different aid stations and different pourers of water make up a whole lot of inconsistency of how much water each cup gets. One way around this is to closely examine the cup, drink the amount in the cup, and then fill it to the difference that it was lacking from the cooler. This, however, isn’t very conscience of your race chip-time, so just be happy that you got that half a cup of water. You could also grab two cups and figure out how much water you got.
  • Collisions at the water/aid station – I was running my third half marathon and I was coming into the water aid station for a cup of water. You would think that you slow down to a brisk or average walk grab a cup of water and keep moving, staying on the right side of the course. Well, I slowed down to a brisk walk grabbed my cup and slammed into the back of the person in front of me. The ice-cold water showered her in the 45-degree run. I heard a shriek…she wasn’t very happy.
  • Water/aid stations could run out of water – Yes, it is rare for a station to run out of water, but it has happened to me one time during one of my half marathons. If you’re a slow runner and the race is extra hot, this could happen at one of the last water/aid stations.

Don’t drink too much water

You typically don’t need more than 30 ounces of water per hour unless you’re running in ultra races or ultra hot or humid weather conditions. If you drink too much water you can induce hypernatremia. Hyponatremia is when you’re body absorbs so much water that your body eventually dilutes all of the sodium in your blood. Hyponatremia is rare but it can be fatal. Signs of Hyponatremia are vomiting, disorientation, headache, confusion, and muscle weakness and cramps.1

What other ways can I get access to water on a half marathon racecourse?

  • Staged Freinds in race
  • Water aid stations
  • Hydration belt – bottles
  • Hydration pack – bottles
  • Hand water bottles
  • Sometimes at races, you’ll run by people’s houses and they will have tables set up with refreshments (maybe it’s a Texas thing?).

How much water does my body need per hour of exercise?

Your body needs between 13 and 27 fluid ounces (0.4 and 0.8 liters) of water per hour of exercise2. The values could vary between individuals due to the amount of sweat lost and how the temperature during the race.

Helpful conversion tables

Hydration pack / water bottle 1 gulp = about 1 fluid ounce

1 cup = 8 fluid ounces

8 fluid ounces = 0.24 liters

0.5 Liters = 17 fluid ounces of water

1 Liter = 34 fluid ounces of water

1.5 Liters (34 + 17 fluid ounces = 51 fluid ounces which are nearly right in the middle of 20-30 fluid ounces per water)

1 Liter = 2.2 pounds of weight

1 Liter is magically 1 Kilogram

How to carry water for half marathons?

I’ve tried multiple ways to carry water during the race and I always fall back on carrying a lightweight hydration vest. Hydration packs can carry between 1 and 4 liters of water. For a half marathon race, you’ll probably need somewhere between 1 and 2 liters of water. This is dependent upon how long you’ll be on the racecourse.

My preferred method is to carry the water on my back in a hydration pack that can carry up to 2 liters of water. I’ve owned four to five CamelBaks and my favorite version of the CamelBak is the Ultralight CamelBak. It’s expensive, but it really is ultralight. There are several other hydration packs out there that I’ve tested, but the Camel Bak is made of high-quality material. Also, I’m a larger framed guy (broad shoulders) so it wasn’t easy finding a hydration pack that fit my frame well.

How much water should I drink during a half marathon race?

I try to drink at least one 12 oz bottle leading up to the half marathon race. This doesn’t mean that I get to the starting line and chug it down in 5 seconds. I sip on the 12 oz bottle until it’s finished prior to the race.

Since I drank 12 fluid ounces of water I don’t start drinking until mile 3 (about the 5K mark on the racecourse). At mile one I will drink between 3 and 4 gulps of water (1 gulp of water is approximately 1 fluid ounce). I will do this every mile up until mile 12. At mile 12 I might take a couple of extra sips for a total of 5 to 6 gulps then no more drinking until I finish the race.  If I continued this pattern through the entire race I would end up drinking a total between 36 and 48 fluid ounces (1 and 1.5 liters) of water.

  • 1  3-4 gulps (3-4 oz of water)
  • 2  3-4 gulps (3-4 oz of water)
  • 3  3-4 gulps (3-4 oz of water)
  • 4  3-4 gulps (3-4 oz of water)
  • 5  3-4 gulps (3-4 oz of water)
  • 6  3-4 gulps (3-4 oz of water)
  • 7  3-4 gulps (3-4 oz of water)
  • 8  3-4 gulps (3-4 oz of water)
  • 9  3-4 gulps (3-4 oz of water)
  • 10  3-4 gulps (3-4 oz of water)
  • 11  3-4 gulps (3-4 oz of water)
  • 12  3-4 gulps (3-4 oz of water)

Is there any easier way?

When I ran my first couple of half marathons I ran with my CamelBak Circuit (affiliate link to Amazon). This pack holds 1.5 liters of water which is exactly perfect for my hydration needs on the half marathon racecourse. I didn’t use the strategy above, where I take 3-4 gulps every 1 mile. Instead, I simply drank to thirst. When you drink to thirst, your mind is a little bit more free from worrying about when to drink next. This can be a good thing and a bad thing, especially if it’s a hot race.

I’m going to leave this up to the individual runner and their preferences. Both methods will hydrate you so when you’re training simply experiment with these methods to find out which one works best for you.

Other things to consider

  • Test your gear – Make sure that you spend time during your training testing your hydration packs (actually wearing this on a long run) before race day. Carry your water bottles with you and see what works and what doesn’. Raceday is not the time to test out new gear
  • Is the race going to be hot? – If it’s going to be hot you might pack a little more water than you usually would for a normal race.
  • Is your half marathon on a trail? – You definitely want to carry more water plus a small first aid kit and maybe a flashlight and ultra-light foldable blanket.

My Recommendations as a coach

I wear a hydration pack for half marathons under these conditions:

    1. I’m unfamiliar with the course
    2. It’s going to be a really hot race (85 degrees and above)
    3. There will be limited water/aid stations on the racecourse (4 or less).

What type of hydration gear should I use for a half marathon?

Check out this post where I give a detailed analysis of the best of the best hydration gear for running half and full marathons.

Running with a smartphone

If you’re wondering what you should do with your smartphone when you run, check out this post I wrote that gives you lots of tips on how to carry your smartphone.

Coach Scott is a published author and RRCA certified running coach (Level 2). He has published over 20 books including, Beginner's Guide to Half Marathons: A Simple Step-By-Step Solution to Get You to the Finish Line in 12 Weeks! (Beginner To Finisher Book 3), which has become an Amazon International #1 bestseller. Scott specializes in helping new runners become injury-free race finishers. He recently completed his 14th half marathon race. 

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  1. Hyponatremia, mayoclinic.org
  2. Stephanie Olzinski, Joshua Beaumont, Meynard Toledo, Amber Yudell, Carol S. Johnston, Floris C. Wardenaar, Hydration Status and Fluid Needs of Division I Female Collegiate Athletes Exercising Indoors and Outdoors, 26 June 2019.
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