How to clean mould out of a hydration bladder

To clean mould out of a hydration bladder, take it apart and scrub the bag, tube and bite valve with warm soapy water and brushes. Then disinfect at the dose your bladder's maker gives. Rinse three times and dry it propped open. If black specks are still in the tube after scrubbing, replace the tube or valve. No maker's bleach dose is strong enough to be relied on to kill mould you have not first scrubbed away.

What counts as mould in a hydration bladder?#

A hydration bladder (makers call it a reservoir) is the soft water bag that sits in a pack. It has a drink tube and a bite valve, the soft mouthpiece you squeeze with your teeth. Mould is a fungus. In a bladder it shows as black, grey or green specks, often in the tube or valve, with a musty taste in the water.

Two words matter here, and Platypus defines both. Cleaning removes residue and "lingering tastes". Disinfecting "is an attempt to sterilize your system". Platypus says to disinfect after dirty water, or if you "notice visible signs of bacteria growth". Visible mould is that case.

One more term runs through this page. Parts per million (ppm) is the strength of a solution. For bleach in water, 1 ppm is 1 milligram of sodium hypochlorite in each litre. That is the active chemical in household bleach.

How to clean mould out of a hydration bladder, step by step#

This is the order the maker instructions add up to. Each step names whose advice it is.

1. Take it apart. Pull the tube off the bag and the bite valve off the tube. Platypus warns that people often clean the bag and forget "the part that actually touches your mouth".
2. Scrub, in warm soapy water. Osprey says warm water and a mild washing up liquid. MSR says hot soapy water. Use a long thin brush for the tube and a wider brush for the bag, as the Platypus, Osprey and CamelBak cleaning kits do. Scrub the valve by hand.
3. Rinse the soap out. Bleach and soap should never meet. The CDC says never to mix bleach with "any other cleaners".
4. Disinfect at your maker's dose. Platypus: 2 to 5 drops of plain bleach per litre, run through the tube and valve, overnight. MSR: one ounce of unscented bleach in a litre of clean water, tube filled, overnight. Osprey: no bleach, use chlorine-free tablets. CamelBak: chlorine-free tablets.
5. Rinse three times. Platypus says three warm water rinses of the whole system after bleach.
6. Dry it open. Shake out the drops, prop the bag open so the sides do not touch, and stand it pointing up (Platypus). Leave the cap off (Osprey).
7. Look again. Hold the tube up to a window. If specks remain, they did not scrub out. Replace the tube or valve rather than soak it again.

Bleach in a hydration bladder: why the makers disagree#

The confusion is real, and it comes from the makers themselves.

Osprey says "DO NOT use bleach or boiling water". Its older Hydraulics manual also says to use cleaning tablets that are "chlorine free".

Platypus says to add "a couple of drops of bleach to water (2-5 drops per liter of water)", fragrance-free and without dyes, and leave it overnight.

MSR is a Cascade Designs brand, like Platypus, and its reservoirs are answered on the same help site. MSR says: "Add one ounce of unscented household bleach... to one liter of clean water." One ounce is 29.6 mL. Two to five drops is about 0.1 to 0.4 mL. So MSR's recipe has about 75 to 300 times as much bleach per litre as Platypus's.

CamelBak gives no bleach dose on any page we could read. Its FAQ says to hand wash reservoirs and to store them clean and dry in the freezer. Its cleaning tablets are "free from chlorine, phosphate, preservatives, and fragrances" and are sold to reduce "taste and odor". A figure of half a teaspoon of bleach per gallon is repeated online as CamelBak's advice. We could not find it on CamelBak's site, so this page does not attribute it to CamelBak.

So which is right? The rule is simple: follow the maker of your bladder. Osprey forbids bleach, and its guarantee terms are its own to set. Where a maker allows bleach, its dose is the one it has signed off for its own film and fittings. The two Cascade recipes differ so much that they cannot both be aimed at the same job. The Platypus dose sits near drinking water strength. The MSR dose sits near surface disinfectant strength. The table below shows how.

What each recipe works out to in parts per million#

Household bleach is 5 to 9 percent sodium hypochlorite, according to the CDC. A drop is not a fixed size. The EPA's own table calls 16 drops a quarter teaspoon and 12 drops an eighth of a teaspoon. That makes one drop 0.05 to 0.08 mL, and we use that range.

Two notes on method. We treat the percentage on a bleach label as grams per 100 mL. And the figures are sodium hypochlorite. Counted as chlorine, as the Food Code counts it, they are about 5 percent lower. That is less than the rounding here.

What the numbers say#

Read down the table and three things stand out.

Platypus's dose is drinking water strength. At 5 to 35 ppm it runs from about the EPA's emergency water dose to three or four times it. Even at its top it is below the Food Code's lowest strength for a sanitiser at room temperature, 50 ppm. And the Food Code applies a sanitiser only "after being cleaned". The overnight soak is far longer than the Food Code's 10 seconds, but no source here tested how far time makes up for strength.

MSR's dose is surface disinfectant strength. At 1,400 to 2,600 ppm it is a bit stronger than the CDC's own recipe for disinfecting hard surfaces.

Nothing reaches the spore-kill figure. The one study figure for killing mould spores outright is 24,000 ppm, about 10 to 17 times MSR's dose. That figure was for spores on test surfaces, not for mould grown into a tube. No maker recommends anything near it for a bladder.

This is why the order of the steps matters. The bleach is there to finish a clean surface, not to dissolve growth. The EPA says it plainly for mould at home: "it is not enough to simply kill the mold, it must also be removed." In a bladder, removing means brushes.

A worked case: black specks in a 2 litre bladder#

Take a 2 litre bladder that sat for three weeks with a sports drink residue in it. Suppose there are black specks along the inside of the tube and a musty smell in the bag.

Clean first. Pull the tube and valve off. Scrub the bag with warm soapy water and the wide brush. Push the thin brush through the tube from the valve end, which Platypus says is the easier way in. Rinse until no soap foam shows.

Then check the tube. Hold it up to the light. Say the specks in the bag are gone, but a few remain in the tube. Those have not scrubbed out, so the tube is the part to replace.

Then disinfect, with your maker's numbers. On a Platypus bag, 2 litres takes 4 to 10 drops of plain bleach. That is about 0.2 to 0.8 mL, for the same 5 to 35 ppm as in the table. On an MSR reservoir, 2 litres takes 2 ounces, about 59 mL, for about 1,400 to 2,600 ppm. Fill the tube, close the bag, and leave it overnight.

Then rinse and dry. Empty it, rinse three times with warm water, then stand it pointing up and propped open. Once it is dry, it can go in the freezer, as CamelBak suggests.

On an Osprey bag the bleach step is skipped. Scrub, use chlorine-free tablets, rinse and dry.

Other cleaners: baking soda, lemon juice, tablets and hot water#

Baking soda and lemon juice is a cleaning recipe, not a disinfecting one, in Platypus's own terms. It is for a "lingering taste" after spirits or a sugary mix. Platypus uses 1/4 cup of baking soda per 3/4 cup of water, shaken through the tube, then 1/4 cup of lemon juice. The mix fizzes and builds pressure, so Platypus says to open it pointed away from you. Shake and vent three times, then soak for 20 minutes and flush three times. MSR gives the same recipe "per liter".

Never follow it with bleach before rinsing. Lemon juice is a cleaner, and the CDC's rule is never to mix bleach with other cleaners.

Cleaning tablets from CamelBak and Osprey are chlorine-free. CamelBak sells its tablets to reduce taste and odour. Neither maker, on the pages we read, claims they kill mould.

Hot water splits the makers again. Osprey says not to pour boiling water in, because it "can damage the reservoir and will void your Guarantee". Cascade's own off-taste advice pours a tablespoon of baking soda in "a couple liters of boiling water" into its bags. That is fine for a Cascade bag and wrong for an Osprey one. Check your maker before using hot water.

How to stop mould coming back#

Rinse and dry after every use. That is Platypus's routine advice. Rinse every time after drink mixes, which Platypus says "can also allow for bacteria growth". If you filled it from a stream without treating the water, disinfect it at home. The water treatment guide covers how to make that water safe in the first place.

Dry it the way the maker tested. Platypus says it found the bag dries fastest pointed up, with the sides held apart by a spoon or a bag-drying rack. Its bags are "UV-safe" in sun. Osprey says to leave the cap off for drying and for storage.

Do not store it with water in it. Cascade says it does "not recommend storing your reservoirs for long periods of time with water in them". Store the bag empty and dry, in the same cool, dry spot as the rest of your kit; the storage guide explains why damp and heat are the enemies.

Or store it in the freezer. CamelBak says freezer storage helps "prevent bacteria growth", once the bag is clean and dry.

Deep clean on a schedule. Osprey suggests about once a month for a bladder in regular use.

Can you freeze a hydration bladder with water in it?#

Yes, if you leave room for the ice. Platypus says to fill it "no more than ¾ full", purge the air and lay it flat. MSR says half full, on its side, air purged. Osprey says freezing "will not affect the quality of the reservoir", but an overfilled one can be damaged. Water expands as it freezes, and that is what bursts an overfilled bag.

Freezing is not cleaning. A bag frozen dirty thaws dirty. And a bladder is not a filter: a frozen hollow fibre filter is a different matter, covered in how long a backpacking water filter lasts. Freeze it clean and dry for storage, or part full for a cold drink.

Test it yourself: is it clean?#

Three checks, all with things at home.

1. The light test. Hold the tube and the bag up to a bright window. Look along the tube's length and at the valve's slit. Any dark speck that is still there after a full scrub is a part to replace.
2. The overnight sniff. Close the dry bag with a little air inside and leave it overnight. Open it and smell. A musty smell means something is still growing, or the bag was not dry.
3. The taste test. Fill it with tap water and leave it for a few hours. If the water tastes off, clean again. Cascade notes that minerals in tap water can also give a taste after storage, so compare it with the same water from a glass.

Common mistakes#

Soaking in bleach before scrubbing. No maker's dose is close to the strength shown to kill spores. Scrub first.

Using another maker's bleach dose. Osprey forbids bleach. Platypus and MSR differ by up to 300 times. Use your own maker's figure.

Mixing bleach with lemon juice or soap. The CDC says never mix bleach with other cleaners. Rinse between steps.

Using scented bleach. Platypus says fragrance-free with no dyes; MSR says unscented.

Cleaning the bag and not the tube. The tube and valve are what touch your mouth.

Drying it flat and sealed. The sides stick together and it stays damp. Prop it open, cap off.

Pouring boiling water into an Osprey bag. Osprey says it can damage the reservoir and voids the guarantee.

Mould on fabric is a different problem. How to get mildew out of a tent sets the same bleach arithmetic against tent makers' rules.

Frequently asked questions#

Can you use bleach in a CamelBak?#

CamelBak's own FAQ and product pages give no bleach dose. They say to hand wash the reservoir and sell chlorine-free cleaning tablets. A half teaspoon per gallon figure, about 30 to 60 ppm, is repeated online as CamelBak's advice, but it could not be found on CamelBak's site. Platypus allows 2 to 5 drops per litre, and Osprey forbids bleach.

How much bleach do you put in a hydration bladder?#

Use your bladder maker's dose. Platypus says 2 to 5 drops of fragrance-free bleach per litre, overnight, which works out to about 5 to 35 ppm. MSR says one ounce of unscented bleach per litre, overnight, about 1,400 to 2,600 ppm. Osprey says not to use bleach at all. Always rinse three times afterwards.

Is black mould in a hydration tube dangerous?#

The EPA says dead mould can still cause allergic reactions in some people, which is why it has to be removed, not just killed. If black specks stay in the tube after a full scrub, replace the tube or the bite valve. If someone who drinks from it is sensitive to mould, replacing the whole bladder is the safer choice.

Will vinegar kill mould in a water bladder?#

No bladder maker on this page gives a vinegar dose for mould. Cascade mentions a vinegar and water solution only for removing off tastes. In a laboratory test of undiluted vinegar, it slowed one common mould and did not slow another. Scrub the mould out, then disinfect at your maker's dose.

How do you dry a hydration bladder quickly?#

Shake out the drops, wipe inside with a paper towel if you can reach, then prop the bag open so the sides do not touch. Platypus says standing it pointing up dries it fastest, and its bags can sit in the sun. Leave the cap off, as Osprey advises, and hang the tube to drain.

How often should you clean a hydration bladder?#

Rinse and dry it after every use, says Platypus, and always after drink mixes. Disinfect it after filling it with untreated water. Osprey suggests a deep clean about once a month if you use it often. Cleaning more often costs nothing and stops growth before it starts.

Can you put a hydration bladder in the dishwasher?#

CamelBak says reservoirs should be hand washed only, and Osprey says not to use boiling water. Neither page allows a dishwasher for the reservoir. Wash it by hand with warm soapy water and brushes, then dry it propped open.