Mould in your bottle lid? Here's what to do

You flip the lid over and there it is: black spots under the seal, maybe a bit of slime. Gross, but very common — and fixable.

Why it happens

The rubber seal sits in a tight groove. Every sip leaves a little moisture and residue behind, and a closed, dark, damp space is exactly where mould and slime grow. Rinsing under the tap never gets in there.

How to clean it

1. Take the lid apart as far as the maker allows: seal, valve, mouthpiece.
2. Fill a cup with warm water and drop in a fizzing tablet.
3. Soak all parts for 15–30 minutes.
4. Run a seal brush along the groove and through the channels.
5. Rinse everything well with clean water and let it air-dry before putting it back together.

When to throw it out

If spots stay after a few cleans, or the seal is cracked or sticky, replace the seal or lid. Some stains soak deep into soft rubber.

Keep it from coming back

• Pop the seal out once a week.
• Let the lid dry fully before closing the bottle.
• Fizz the lid along with the bottle every week.
• Don't leave sugary drinks sitting in the bottle overnight.