The green buildup you’re seeing in your Brita pitcher is almost certainly common green algae, and it’s not dangerous to most people. It looks unpleasant, but true green algae (as opposed to blue-green algae, which is actually a type of bacteria) does not produce toxins. That said, any microbial growth in your drinking water is a sign that your pitcher needs cleaning, and in rare cases what looks green could be something worth taking more seriously.
Why Algae Grows in a Brita Pitcher
Algae are microorganisms that need just three things to thrive: water, warmth, and light. A Brita pitcher sitting on a kitchen counter near a window checks all three boxes. Even indirect sunlight filtering through a translucent pitcher is enough to fuel algae growth over time, especially in warmer months or kitchens that stay above room temperature.
Brita filters remove chlorine from tap water, which is the very chemical that keeps algae and bacteria in check. Once that chlorine is gone, any algae spores that enter through tap water, airborne dust, or contact with hands can multiply freely. The longer filtered water sits at room temperature, the faster that green film appears on the walls of the pitcher, around the lid, and sometimes on the filter housing itself.
Green Algae vs. Blue-Green Algae
This distinction matters. True green algae is a simple plant-like organism. It’s the same stuff that coats rocks in a stream. It doesn’t produce harmful toxins and isn’t known to cause illness in healthy adults, though drinking water visibly clouded with any microorganism isn’t ideal.
Blue-green algae is a different story entirely. Despite the name, it’s not actually algae. It’s cyanobacteria, a type of bacteria that can produce several dangerous toxins. According to the CDC, swallowing cyanobacterial toxins can cause stomach pain, vomiting, diarrhea, headache, muscle weakness, dizziness, and even liver damage. Skin contact alone can trigger rashes, eye irritation, and sore throat. Cyanobacteria can turn water green, blue-green, or murky, so color alone isn’t a reliable way to tell what you’re dealing with.
In a household Brita pitcher, cyanobacteria growth is unlikely. These bacteria typically bloom in warm lakes, ponds, and slow-moving rivers where nutrient levels are high. Municipal tap water is treated to eliminate them before it reaches your faucet. Still, if the growth in your pitcher looks unusually thick, has a blue-green tint, or the water smells foul, discard the water and thoroughly clean the pitcher before using it again.
When It Could Be a Problem
Even harmless green algae signals that other microbes may be growing in your pitcher too. Bacteria, mold, and biofilm (a slimy layer of mixed organisms) can build up alongside algae, particularly when a pitcher hasn’t been washed in weeks. For most healthy adults, small amounts of these organisms pass through the digestive system without issue. But people with weakened immune systems, young children, and elderly adults are more vulnerable to waterborne illness from bacterial contamination.
If you’ve been drinking water from a pitcher with visible algae and haven’t experienced any stomach upset, you’re fine. The growth was almost certainly benign. But continuing to drink from a visibly contaminated pitcher isn’t worth the risk when the fix is so simple.
How to Clean Your Pitcher
Disassemble the pitcher completely: remove the lid, filter, and any internal reservoir. Wash every non-filter component with warm water and dish soap, using a bottle brush or sponge to scrub away any green film. Pay extra attention to the underside of the lid, the spout area, and any grooves or seams where algae likes to hide.
For stubborn buildup, soak the plastic components in a solution of one teaspoon of white vinegar per cup of water for 15 to 20 minutes, then scrub and rinse thoroughly. You can also use a diluted bleach solution (about one teaspoon of unscented household bleach per gallon of water), but rinse several times afterward to remove any residual taste. Never put cleaning solutions through the filter itself. If your filter has visible algae on it, replace it.
Preventing Algae From Coming Back
The single most effective thing you can do is store your Brita pitcher in the refrigerator. Cold temperatures dramatically slow algae growth, and the fridge is dark, cutting off the light algae needs to photosynthesize. A pitcher stored in the fridge will stay clean far longer than one left on the counter.
Beyond refrigeration, a few habits make a big difference:
- Wash the pitcher weekly. A quick scrub with dish soap once a week prevents biofilm from gaining a foothold.
- Replace filters on schedule. Brita Elite filters last about 120 gallons, or roughly six months of typical use. An indicator light near the spout turns red when it’s time. Old filters lose their ability to reduce contaminants and can themselves become breeding grounds for bacteria.
- Don’t let filtered water sit for days. If you won’t finish a full pitcher within a day or two, fill it with less water each time. Stagnant filtered water loses its freshness quickly.
- Keep the pitcher away from windows. If refrigerator space is tight, at minimum store the pitcher in a dark cabinet or a spot that never gets direct or indirect sunlight.
Is It Safe to Keep Using the Same Pitcher?
Yes. Algae doesn’t permanently contaminate plastic. Once you’ve scrubbed and rinsed the pitcher thoroughly, it’s perfectly safe to refill and use again. If you notice deep scratches on the interior walls where algae keeps returning despite cleaning, those scratches are harboring organisms in places your sponge can’t reach. At that point, replacing the pitcher (they’re inexpensive) is the simplest solution.