Water Filter Turned Pink – What Is It And Is It Harmful

If you have noticed your water filter is turning pink or reddish with some strange particles, you may be concerned your water is not safe to drink. In fact, you may have also noticed this pink slime in other wet areas of your house and wondered where it comes from.

Water filters and filtration systems develop a pink slime or stain because of the bacteria Serratia Marcescens. The bacterium can contaminate water filter pitchers, faucet filters, dispensers and bottles. Serratia Marcescens affects surfaces that are regularly damp or moist, and produces a red and pink pigment at room temperature. It is a leading cause of pneumonia and bloodstream infections in hospitals worldwide.

This article will give you all the details on why your water filter is turning pink and where your filter pitcher, bottle, dispenser or faucet filter is most susceptible to bacterial contamination. But most importantly, this post explains how to remove the pink slime/stains and prevent your water filter turning pink in the future.

Why is my water filter turning pink?

Serratia marcescens is an opportunistic bacterium that thrives wherever there are phosphorous or fatty substances. So, anywhere there is water, dampness and a lack of chlorine there is a possibility of this bacteria growing and that includes your water filter.

In fact, Serratia Marcescens needs almost nothing to survive in these wet environments.

The bacterium has a light pink color that can also be dark red. This color reflects the age of bacterial colonies that live in water, soil, and the digestive tracts of mammals, including humans.

Where does it form in your water filter?

Serratia marcescens can affect all surfaces where moisture and dampness are found. This includes areas of your water dispenser, pitcher, bottle and faucet filter.

The inside of your lid or your filter housing is particularly susceptible to bacteria growth.

When we replace our filter, we don’t always clean around the housing carefully and it can become the perfect breeding ground for bacteria, especially right between the slot or grooves where the filter sits in. These tiny spaces provide an ideal home for the bacteria to grow in.  

Be sure to clean and dry areas of your water dispenser and pitcher where stagnant water and dirt could sit to help prevent this bacterium from taking hold.

When we grab our water pitcher, we also don’t realize that our hands may be dirty and wet, this can cause bacteria to transfer and grow on the inside of the pitcher handle – usually in the joining corners connecting the pitcher or dispenser to the reservoir.

The areas of water filtration systems that are most likely to become contaminated with pink slime or stains are provided in the table below:

Filtration systemContamination sites
Filter pitcherFilter
Filter housing area
(Slots, threads and grooves)
Inside of pitcher handle
Underside of lid
Inside of lid
Spout / Tap
Filter bottleFilter
Grooves / threads of bottle
Straw /spout
Faucet filterFilter
Filter connection point
(Slots and threads)

We also place our pitcher on various surfaces that can be contaminated with household dirt and moisture. Be sure to dry your pitcher and dispenser thoroughly to create an unfavorable environment for the bacteria to grow.

Most filters have approximately 2 months life cycle or 40 gallons (depending on your brand), and remove chlorine, zinc, copper, cadmium and mercury but are less effective at removing bacterial contaminates.

Bacteria does not bind to carbon-activated filters so they either make their way through to your glass of water or get stuck in your filter.

Most water filters are activated carbon-based, which also removes the chlorine from water. Chlorine is very effective at killing bacteria and by removing it, bacteria can grow unimpeded once your water has passed through the filter.

How to remove the pink film of slime (Serratia marcescens)

It may be challenging to exterminate the bacteria once it has taken hold, especially if the pink residue has already established itself extensively in an area.

However, treatment is possible for small contaminations:

Treatment by DIY

In general, the pink slime is resistant to standard household cleaning methods and requires special attention. Local pink slime occurrences can usually be treated by following these steps:

  1. Wash hands thoroughly before handling your filtration device
  2. Mix 1 cup of baking soda to 1.5 cups water, along with 2 teaspoons of liquid soap.
  3. With a soft brush, scrub the pink slime contamination away from the surface with the baking soda mixture.
  4. Dispose of any residue by rinsing it with water.
  5. Afterwards, the area needs to be sterilized to eliminate any remaining bacteria. Spray all affected surfaces with a mix of 50/50 warm water and household bleach.
  6. After letting the bleach solution rest for 10 minutes, lightly scrub it with a brush.
  7. The residue should be washed away with water and dried with a clean towel (where possible)
  8. If the filter itself has developed the pink slime or stain it must be discarded immediately and replaced.

To prevent bacterial contamination in the future it is important to take the following steps:

  • Always wash your hands before handling your filtration device. Use soap and wash your hands for at least 30 seconds.
  • Clean your pitcher, dispenser, bottle and lid regularly – at least once a month for the pitcher and dispenser and daily for a filter bottle
  • We also recommend washing the pitcher, dispenser, bottle and faucet filter every time you replace the filter.
  • Keep the spout (tap or straw) of the filter clean.
  • Make sure the spout is sealed tightly after use.
  • Do not drink directly out of the pitcher or dispenser. Pour the water into a glass.
  • Replace the filter frequently, according to manufacturing instructions.

Is Professional Remediation Required?

Serratia marcescens contaminations do not require professional treatment unless the contamination extends more three square feet. In which case, you should contact a bacteria remediation specialist and get professional treatment. These types of contaminations are more commonly found in a bathroom, laundry or basement.

Will a water filter remove Serratia marcescens?

Water filters cannot typically remove bacteria from water. The Serratia marcescens bacterium cannot be eliminated entirely once they are established. The best way to remove the pink slime or stain is to discard the filter immediately, and thoroughly clean the surfaces affected by treating them with chlorine bleach.

Is Serratia marcescens harmful to drink?

Recent studies have found that Serratia marcescens can cause disease in a small proportion of individuals.

Several US water companies add a small amount of chlorine to ensure their water is safe for consumption, free of parasites like Serratia marcescens. However, if you leave the water to stand for 30 minutes or longer, the chlorine disinfectant can evaporate into the air and can become susceptible to Serratia marcescens.

In fact, Serratia marcescens has been known to cause urinary tract infections, wound infections, and other medical conditions such as, endocarditis, osteomyelitis, septicemia, wound infections, eye infections, and meningitis.

Brita water pitcher turning pink

Brita water filter pitcher turn pink because of the airborne bacteria Serratia marcescens. The bacterial contamination is a result of infrequent or improper cleaning of the filter and filter housing area, or the filter not being replaced regularly.

It is easy to overlook these small chores, however Brita filter pitchers must be cleaned every 2 to 3 weeks. Brita filters should be replaced every 2 to 6 months depending on which Brita Pitcher you have:

  • Brita Standard (White) Filter: Every 40 gallons (about 2 months)
  • Brita Longlast (Blue) Filter: Every 120 gallons (about 6 months)
  • Brita Stream (Gray) Filter: Every 40 gallons (about 2 months)

Cleaning your Brita water pitcher

Cleaning a Brita water filter pitcher is very easily achieved.

Pitcher Disassembly:

  • Pour out any remaining water inside the pitcher and disassemble.
  • Brita filters have a special tank that must be separated.
  • The screen must be changed if it has not been done previously. Place it on a clean surface after rinsing with warm water to prevent it from becoming contaminated
  • Invert the vase so the water fills the bottom and the base becomes heavy. Water should push out the inserted plastic.

Pitcher cleaning:

  • Prepare a cleaning solution by mixing 1 tablespoon dish soap and 1 cup warm water.
  • The lid and its reservoir should be soaked for at least 30 minutes in the solution.
  • Scrub each piece individually until a squeak cannot be heard and each piece is clean.
  • The reservoir can also be washed with a mild detergent and warm water, followed by a gentle dry with a soft towel.
  • Place the pieces/components into a bowl of white vinegar (one teaspoon) blended with water (one cup), then scrub the parts with this solution.
  • The reservoir and lid should both be thoroughly rinsed in water and dried to avoid bacterial growth again. Racks are recommended for storing the pieces. A dishtowel can also be set with the part upended.

Pitcher reassembly:

  • The Brita filter may need to be soaked beforehand, depending on which model you are using. With the latest versions of Brita filters, you don’t necessarily need to soak them before washing them as in the older models. To be sure the Brita filter is cleaned correctly, consult the instructions on your filter.
  • Place the new filter in to the filter housing area and replace all of the parts together.
  • Fill the pitcher’s reservoir and disperse any remaining carbon dust with the water. A minimum of two flushes should be repeated. When the water is clear, it indicates that it is carbon-free and can be reassembled.


While infection of the Serratia marcescens bacteria is rare and easily rectified, this does not mean we should skip on cleanliness in our households. Do a thorough clean of your water filters and containers regularly to avoid any bacterial contamination.

Keep areas susceptible to moisture and dampness dry. Use bleach in those areas to kill germs and bacteria. Don’t forget to rinse these areas after they have been cleaned with bleach.

Always make sure what you are drinking is safe. Remember a healthy body means a healthy mind, which makes a healthy you.

Happy hydrating!

Theresa Orr

Theresa Orr is an Earth Scientist who specializes in determining past climates from rocks using geochemistry. Her passion for clean water drives her to breakdown the science to provide easy to understand information that everyone can read.

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