Wash your hydration bladder. If not right now, tonight. If not tonight, tomorrow. If not tomorrow, well, how’s your immune system? A few summers ago, I pitched my hydration waistpack into the back of my truck and it just kinda festered. It wasn’t full of water, but I hadn’t dried it out before I forgot about it, and, as I learned when I picked it back up and took a quick sniff of the drinking tube’s business end, life had found a way to take hold there.

What kind of life? Well, I don’t own a microscope, nor am I a microbiologist, but I found studies that show reusable water bottles grow bacteria like Staphylococcus aureus and E. coli very easily. Norovirus, a pathogen that causes particularly nasty cases of food poisoning, loves the water bottle environment. Not to mention fungi and molds that grow in the pores, cracks, and crevices of water bladders and bottles. So, yeah, gross. For years, I washed my water bottles only when they smelled bad. I’ve never become ill from their use, or at least if I did, I attributed that illness to another source. But now that I know what grows in there, I wash them much more carefully and frequently.

So before I used my hydration bladder again, I decided to clean the thing properly, probably for the first time since I’d owned it. Not just dunk the bite valve in boiling water, not just rinse the thing with hot water, which is what I normally did, but an actual scrub. Now, you can buy a cleaning kit from companies like CamelBak if you want and feel like spending extra money but you don’t need to do that. All you need are some basic kitchen supplies. You don’t even have to use soap. These days I use a hydration bladder daily on mountain bike rides, so the following is my, oh, bi-monthly cleaning regimen. My drinking tube smells clean, the water tastes fresh, and I’m confident nothing overly funky is growing in there.

Here’s what I do.

• Gather my ingredients. I typically use bleach, baking soda, and lemon juice. I have tried substituting vinegar for bleach, but I had a hard time getting the pungent vinegar odor out of the bladder. I prefer not to use dish soap because I never feel confident I’ve thoroughly rinsed, plus, I know that bleach is killing all the pathogens and mold. Baking soda increases the effectiveness of bleach by, if memory serves, weakening the cell walls of bacteria, so I use them both. My bladder is 1.5 liters, so I use one teaspoon of bleach and one tablespoon of baking soda.

• The first thing I do is heat about a liter of water to 140 degrees, the maximum my bladder can tolerate according to the manufacturer (Hydrapak). I pour that in the bladder along with the baking soda. Then I use a bottle brush to scrub the inside of the bladder. A slick biofilm can grow on the porous surface of plastic, harboring germs, so I make sure to try to break that up with scrubbing. Then I add the bleach, shake the bladder, and hang it up with the drinking tube dangling. I squeeze the bit valve until water squirts out to be sure the solution is running through the tube, then I let it hang for about 30 minutes. Or an hour, I’m not that picky.

• I then drain the bladder and remove the drinking tube. I soak the tube and the bite valve in a mixture of lemon juice and water to clean the outside. I rinse the bladder thoroughly, then turn it inside out and place it open on my dish rack to dry. It’s crucial to let it dry out all the way if you intend to store it, otherwise, that moisture can mold, things can grow, and you’ll have to start all over again.

• If, like me, you use a bladder too often to let it dry out completely between uses, you can store it in the freezer which will halt any growth of microbes, and has the added bonus of being nice and frosty when you fill it, a joy on a hot day.