How to Choose a Hydration System for Trail Running

Introduction to the different hydration systems available in the market, the pros and cons of each, and how to choose the best one for your next trail race or training session

Hydration systems for trail running. Photo: Salomon
Endurance tests that can exceed 24 hours, thin air, scorching sun, temperature drops, routes through remote areas with no easy way out. You can find all this and much more on a trail race. So if proper hydration is an important factor in any sport, it is crucial when it comes to trail running.

Hydration in trail races has to be effective: the systems must not hinder your movement and they have to be accessible so that you can drink on the run without making a stop. There are a range of hydration systems on the market, and all are integrated into the different models of backpacks and waist packs designed for trail running. Equally important as knowing how to choose your trail running backpack, you should also know the different types of hydration systems and the pros and cons of each.

Vest-style pack with water bottle on the should strap; Backpack with water bottle on the shoulder strap and internal hydration bladder.

Backpack with Flexible Reservoir

These are the classic reservoirs (also called bladders) located in an inside pocket of the backpack that has a flexible tube for drinking. These were the first designs to hit the market and featured the ability to drink without having to stop. They were modeled directly after cycling backpacks, and although their use in climbing has taken hold, they are increasingly less popular with runners. Why? There are several reasons:
  • As an internal system, it is impossible to see how much water is left, making water intake more difficult to regulate.
  • You have to take off your backpack to refill, wasting time.
  • When you put the pack back on, the water cools down your back, which can cause problems and injuries in certain circumstances.
  • In small-volume packs for short- and medium-distance trail runs, the bladder occupies practically the entire pack.
Are flexible reservoirs still used? Yes, mainly for ultra races, long runs in the mountains in areas where water is scarce, and in survival challenges, activities in which larger-capacity backpacks or vests in which the bladder can be incorporated are used. They are combined with the most common water-carrying systems, using the larger-volume reservoir as a backup in many cases: flat, integrated into the pack and carried along the back, the bladder does not limit movement like a bottle or a larger-volume reservoir inside the backpack.

Example of a backpack with a dual system: integrated bladder and water bottles on the straps.
Water Bottles – Hard or Soft
Bottles are the most commonly used solution in today’s trail running world. Trail running waist packs, vests and backpacks are designed to seamlessly carry these bottles, those with a low-carrying capacity and those that also have an internal bladder. And bottle designs have been adapted to allow quick hydration without stopping to take a drink. With a backpack, the most common solution is to carry the bottles in the shoulder strap pockets designed for this purpose. With a twist of the cap and a tilt of the head you reach the mouthpiece and drink without stopping. Bottles with an extension tube are becoming increasingly more popular; they make hydration easier, since –like the tubes used with backpack bladders– the mouthpiece is located directly next to the mouth.

Even the smallest running waist pack is designed to carry a water bottle. Photo: Salomon
There are two types of water bottles: rigid and soft. While hard bottles continue to be used, soft bottles are more popular today. Since both have their pros and cons, we recommend giving both a try to see which one you personally prefer.

Hidrapak soft flask with extension tube.
Pros of soft water bottles
  • Ultra-lightweight
  • They can be folded up when empty and take up little space in the backpack, unlike hard bottles.
  • Carried in pockets on the straps (the most common and comfortable system), drinking requires little effort: simply squeeze and drink (along with its light weight, this is the key feature that makes their use so popular).

Cons of soft water bottles
  • Less durable than their rigid counterparts.
  • More difficult to fill. There’s no issue if the water source comes from above (a fountain, for example), but they float if you have to replenish the bottle from a horizontal surface (like a river), and you have to submerge the bottle to get the air out first.
  • More difficult to carry in a backpack. There’s no problem when they’re empty and folded up, but unlike hard bottles, their flexibility makes getting them into a fully packed backpack more difficult.

The pros and cons of hard water bottles are exactly the opposite:

Pros of hard water bottles
  • More durable.
  • Easier to fill.
  • Easier to pack.

Cons of hard water bottles
  • Heavier.
  • They take up the same amount of space when both empty and full.
  • Drinking requires more effort when the bottles are carried in the straps.

Raidlight hard water bottle.
Handheld Water Bottle
Another option is the handheld water bottle, which is a type of glove with a bottle attached to the palm. This system makes it easy to carry the bottle in your hand and drink naturally without having to worry about holding on to the bottle while you run. This system is hardly used on mountain runs in Europe, but is a popular solution in the United States.

Salomon handheld water bottle system
Soft-flask Compatible Water Filtration System
One of the problems that you will experience on mountain runs is that safe drinking water is not always available, yet stopping to purify water can be slow. To solve this problem, Katadyn has launched a brilliant invention, the Katadyn Befree, a filter that fits into any of the soft flasks of the popular 42 mm thread Hidrapak. With a hollow fiber of only 0.1 micron, the filter is completely effective against microorganisms like protozoa, microbial cysts and bacteria like Escherichia coli (e-coli), Enterococcus, Giardia, and Pseudomonas aeruginosa, as well as sediments. Its filtering feature paired with a soft flask shape specifically designed for trail running makes it an excellent system for the mountains, giving you the freedom to drink water safely and quickly. At the same time, it is more comfortable than direct drinking tubes during a race.

The Befree even offers a version with a soft flask included.

Hydrapak Befree, filter and bottle.
The problem of trash generated on mountain races led many organizations to make the decision to prohibit plastic or cellulose cups at the water points. The solution? Requiring runners to carry a type of cup that several brands began to manufacture in response to this need.

They are ultralight, of course (weighing it at only 9 grams), and come with a ring that makes it easy to attach them to your backpack, keeping the cup within reach at all times and making it easier to use when drinking from rivers, etc.

Salomon cup for racing
The cup can be used at the race’s water stations, although it can also be used to easily and quickly drink from fountains, ponds, and rivers and streams, helping you save your water supply.

Unfortunately, and in spite of major advances, it has been impossible to make plastic bladders that don’t pick up the flavor, however faint, of anything other than water. In this aspect, metallic bottles are still superior. If you’re planning to drink anything other than water on your race, we recommend carrying a bottle or reservoir exclusively for water, and another for other drinks.

We always recommend storing bottles and bladders in the freezer. Why? A bit of moisture is always left inside after use, which can easily grow into mold if left out. Freezing this moisture keeps mold from growing.

Now that you know the different options available, we invite you to explore the wide range of hydration systems at our online store.

Flexible Reservoirs / Bladders

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Hard and Soft Bottles and Flasks

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Water Purification Systems

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You can also contact our customer service department for personalized advice.

How to Choose your Trail Running Pack or Belt

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