Since they first made their commercial appearance in the late 1980s, hydration packs containing reservoirs, also called bladders, have become the de facto method of transporting water for hiking, backpacking, mountain biking, trail running and just about any outdoor activity that necessitates ample fluids. 

As the story goes, CamelBak was born when Michael Eidson was going to participate in the Hotter ‘N Hell 100 bicycle race. Eidson filled an IV bag with water medical tubing and slipped the bag into a tube sock and dropped everything into the back of his bike jersey. Numerous manufacturers now produce these hydration packs, including Osprey, Hydrapak, Gregory and Platypus, just to name a few. And while they may each offer varying features, the one commonality is that they require proper cleaning, drying and storage.

Cleaning a hydration bladder isn’t likely the first thing you think about after a full day of riding, a weekend backpacking trip or a long run on a hot day, it should be. “The primary reason to keep your reservoir clean and dry during storage is so there is no mold growth,” says Steven Nadler, Vice President of Product and Marketing at CamelBak. “The combination of moisture, darkness, temperature and time can create mold.”

Below, what reservoir manufacturers suggests you do to properly clean a hydration pack. 

After every use: Rinse and dry

CamelBak recommends you thoroughly rinse and dry your reservoir after each use, as you don’t want there to be any residual water in the reservoir when you store it. After rinsing the reservoir, you’ll want to hang it upside-down to dry completely. 

Because the reservoirs are mostly flat, keeping them open while they dry and drain can be accomplished using:

• Kitchen whisk: Insert the whisk into the reservoir to keep it open, and prop the whole thing, reservoir opening down, in a drying rack until thoroughly dry.
  
• Reservoir hanger: Some brands offer a hanging device that keeps the reservoir open allowing air to circulate.
  
• Paper towels: Stuffing the reservoir with paper towels keeps it open while also absorbing the residual moisture. 
  

Pro tip: If you don’t have time to dry completely between uses, placing the reservoir in the freezer will also prevent mold growth.

After several uses: Deep-clean the reservoir

While the rinse and dry is great for day-to-day use, after several uses, you’ll need to dig a little deeper into the cleaning process. Below are some of the other recommended cleaning solutions, but check with your specific manufacturer for its best suggestion. 

• Mild dish detergent: Add a small amount of dish detergent to warm water. Using a cleaning brush to get into crevices and a straw brush to scrub out the tube.
  

• Bleach: Add 2 to 5 drops of household bleach to each liter of water and let it sit in the bladder and straw for five minutes to kill both bacteria and viruses that may be lingering in the recesses. 
  

• Baking soda: This common household essential works to eliminate odors. For every liter of volume to your reservoir, combine ¼-cup of baking soda to ¾-cup of water. Let soak for five minutes and rinse.
  

• Dishwasher: Hydrapak-branded reservoirs are reversible. Once turned inside-out, the reservoirs are top-shelf dishwasher-safe. Bonus: They dry quicker after use if reversed.
  

• Cleaning tablets: According to Nadler, “If you’ve been drinking something other than water in your reservoir, like electrolytes or energy drinks that may contain sugar, we recommend a deeper cleaning using reservoir-cleaning tablets.”