Mold in Water Bottle: How to Clean It (and Your Brita)

Mold and bacteria need water, a little food and time. A bottle gives them all three:

• Water that sits in the bottle, the lid threads, or the straw
• Food from saliva, backwash, and anything other than plain water (sports drinks, coffee, smoothies)
• Time, when the bottle is refilled for days without being washed, or capped while still wet

Bottles do carry germs. NDSU Extension describes a University of Calgary study of 75 schoolchildren's bottles, which found about 9 percent of the bottles contained fecal bacteria and 13 percent of the bottles contained other types of germs from food and saliva.

Where mold hides

Table: Where mold hides in a moldy water bottle.

The extension services agree on the basics. NDSU says to wash your water bottle every day with hot, soapy water. Purdue Extension says to wash your water bottle either after every use or daily if you refill throughout the day.

1. Take it apart. Remove the lid, straw, seal ring and any valves.
2. Wash with soap and hot water. Purdue suggests you fill the water bottle with water and dish soap and soak the other pieces in soapy water.
3. Use brushes. NDSU says to use a bottle brush to get all the nooks and crannies clean. A thin straw brush reaches inside straws.
4. Rinse well.
5. Dry completely before you close it. Purdue says to make sure the bottle is completely dry before reassembling to prevent it from becoming musty.

Can it go in the dishwasher? Check the bottle's label. Even if it's dishwasher-safe, NDSU warns that the dishwasher probably will not clean most bottles thoroughly because of their shape. Hand-scrub the lid and straw either way.

If you already see black, green or pink spots, wash first, then sanitize.

1. Take everything apart, including the seal ring. Pry it out gently with a butter knife or toothpick if needed. Most of the mold is usually behind it.
2. Scrub every piece with hot soapy water and brushes.
3. Sanitize. NDSU suggests you consider sanitizing the bottle with a mixture of 1 teaspoon of chlorine bleach (unscented) per quart of water. The CDC uses the same strength for drinking water containers: mixing 1 teaspoon of unscented liquid household chlorine bleach in 1 quart (4 cups) of water, then waiting at least 30 seconds before pouring it out. Put the lid, seal and straw in the solution too.
4. Rinse and air-dry. NDSU says to let it air-dry completely. The CDC says to let the empty container air-dry before use.

Safety: Use plain unscented bleach, and never mix bleach with ammonia or other cleaners, per the CDC. If you'd rather avoid bleach, see our guides on hydrogen peroxide, baking soda and vinegar vs. bleach, and check what your bottle's maker allows.

When to throw it out

Replace the part, or the bottle, if:

• Mold stays in a seal, valve or straw after scrubbing and sanitizing
• A soft straw or seal is stained deep into the material
• The lid has crevices you can't take apart or reach
• It still smells musty after a full clean and dry

Many brands sell replacement lids, straws and gaskets, which is cheaper than a new bottle.

Filter pitchers get moldy too, in the reservoir, the lid, the spout and sometimes the filter itself.

Consumer Reports explains why: a water-filled carafe can become a breeding ground for microorganisms when left at room temperature, and the bacterial growth may or may not be visible, for example occurring in the spout of the carafe or hidden in the filter. In that 2010 article, it noted that most makers recommend keeping the pitcher in the refrigerator, and quoted Brita's manual: we recommend that you store your Brita system in the refrigerator. If you keep it on the counter, Brita advised you replace any filtered water that has been left sitting for several days or more.

What to do about a moldy pitcher:

1. Remove and throw away the filter if you see mold on it or in the reservoir around it. A filter can't be scrubbed clean inside.
2. Wash every part of the pitcher (reservoir, lid, spout) with warm soapy water and a soft brush. Check your manual on whether it's dishwasher-safe.
3. Sanitize if needed with the same 1 teaspoon per quart bleach solution, then rinse well and air-dry.
4. Install a new filter and prepare it as the manufacturer directs.

How often to replace the filter? The CDC says to maintain and replace all water filters according to the manufacturer's instructions, including pitcher, countertop, refrigerator and faucet filters. Consumer Reports says it's usually every two months or 40 gallons, whichever comes first, and that slow flow means it's likely that the filter is clogged and it's time to replace it. Don't stretch it: Consumer Reports has warned that an overloaded filter may harbor microorganisms.

Table: How to stop a water bottle from getting moldy again.

Metal straws need the same care. Purdue says to wash them after each use, even if you're just drinking water, with a thin brush, and dry them before storing.

Stop using a moldy bottle until it's cleaned. The CDC says mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or skin rash in some people, and that people with asthma or mold allergies may react more strongly. People with weakened immune systems should be more careful; the CDC notes that immune-compromised people and people with chronic lung disease may get infections in their lungs from mold. If you feel sick, see a doctor. A doctor, not a mold test, diagnoses mold-related illness. Our mold exposure and mold allergy guides have more.

A moldy bottle is a cleaning job. But if mold keeps showing up on cups, dishes and food in your kitchen, or on things stored in a cabinet, the room itself may be too damp. The EPA recommends keeping indoor humidity below 60 percent (ideally between 30 and 50 percent). Look for leaks under the sink and around the fridge, and read signs of mold in your house and mold in the refrigerator. If your bottle lives in a hot car, our mold in car guide covers what else can grow there.

If you find mold on walls or cabinets, Texas lets homeowners clean small areas: TDLR says areas of visible mold of less than 25 contiguous square feet can be cleaned up by people who are not licensed. For bigger problems, use a licensed mold testing company to find the source and a separate licensed removal company to fix it, since Texas law says a license holder may not perform both mold assessment and mold remediation on the same project.

Find licensed mold testing companies in Austin or Fort Worth, and mold removal companies in Houston or San Antonio. Browse all of Texas, check any license with our license check, and see how we verify listings.