Pink Mold: What It Is, What Causes It, and How to Remove It

What you are looking at

Six different things turn up pink in a house, and only two are molds. Texture sorts them faster than shade: slime is bacterial or yeast film, fuzz is mold, a stain under a vinyl skin is a dye, and a tint in the water is chemistry.

What you see	Most likely	Tell	Source
Slimy pink to orange-red film at drains, grout, bowl waterline	Bacterium: Serratia marcescens	Slimy; stains come off with a bleach cleanser	North Dakota State University Extension
Glossy coral to salmon spots on shower curtains, toothbrushes	Yeast: Rhodotorula	Smooth and shiny, not fuzzy	University of Adelaide mycology unit
Cream or pink colony that darkens to brown or black	Mold: Aureobasidium pullulans	Pink stage is temporary	University of Adelaide description of Aureobasidium pullulans
Pink or purple tinted growth from a drain	Mold: some Fusarium species	Only a lab can name it	University of Adelaide Fusarium page
Rose blotches showing through vinyl from below	Bacterium: Streptoverticillium reticulum dye	Does not wipe off; it is inside the vinyl	PCI Magazine
Pink or purplish water itself, no film	Chemical: potassium permanganate	Blades said it would pass in days	Town of Blades, Delaware

Other colours: orange mold covers iron staining and slime molds; red mold covers red growth.

Which pink is it? Six questions

Stop at the first yes.

1. Is the water itself pink, straight from the tap, with no film? Ask whether a greensand or permanganate iron filter serves the house or the town. Why this differs from generic advice: no cleaner is needed; Penn State Extension explains that greensand media is coated with potassium permanganate.
2. Is it slimy, at a drain, a grout line low in the shower, or the toilet waterline? Treat it as Serratia. Why: drying matters as much as the product.
3. Is it glossy coral or salmon spots on a shower curtain or a toothbrush? Likely Rhodotorula. Why: launder or replace the item.
4. Is it fuzzy, or are pink spots turning brown or black? Treat it as mold. Why: young Aureobasidium colonies can be pink before they darken, and mold on porous material may have to be discarded.
5. Is the pink under the surface of vinyl upholstery, never on top? Pink stain. Why: surface cleaners cannot reach a dye inside the plastic.
6. Is it on food? Discard the food and clean the container. Why: food rules come from USDA, not from colour.

Serratia marcescens, explained

Giri and colleagues in BMC Microbiology describe Serratia species as Gram-negative bacteria noted for a cell-associated red pigment, prodigiosin, which is why North Dakota State University Extension calls the bathroom film a red substance and readers call it pink.

The pigment is not a fixed trait. In the same 2004 study, a soil isolate stopped producing it above 30 C in nutrient broth but kept producing it at 37 C on a peanut seed medium and up to 42 C on a fatty acid medium. So a colourless film beside the pink can be the same organism: clean the whole wet zone.

Organism	Type	Colour as published	Published growth note	Source
Serratia marcescens	Bacterium	Red pigment, cell associated	Pigment blocked above 30 C in nutrient broth (one isolate)	Giri and colleagues in BMC Microbiology
Rhodotorula	Yeast	Coral red to salmon or slightly orange	46 species in the genus	University of Adelaide mycology unit
Aureobasidium pullulans	Mold (black yeast)	Cream or pink, later brown or black	Optimum 25 C, maximum 35 to 37 C	University of Adelaide description of Aureobasidium pullulans
Fusarium	Mold	Pink in some species, purple in others	Mostly soil fungi	University of Adelaide Fusarium page

What causes pink mold

Every cause on North Dakota State University Extension‘s list comes back to food plus standing water, and NDSU ties growth to chlorine loss. Federal rules set both ends of the dose a utility delivers. Under 40 CFR 141.72, a covered public system’s residual entering the distribution system cannot be below 0.2 mg/L for more than 4 hours. Under 40 CFR 141.65, the ceiling for chlorine and for chloramines is 4.0 mg/L as Cl2.

Water standing in a trap or bowl is no longer topped up from the main, which is why NDSU’s chlorine remark matters most in a guest bathroom.

Cause	What NDSU says	What to change
Soap, shampoo or feces residue	Food: phosphorus or fatty substances	Rinse residue off after use
Water that sits	Chlorine dissipates and the film settles in	Dry tubs and sinks; flush seldom-used toilets
Activated carbon filter on the line	Removes chlorine, which may support growth	Expect more cleaning downstream of the filter
Construction or remodelling	NDSU notes it appears during or after	Clean new fixtures early, before film builds
Summer with windows open	More common then, per NDSU	Run the fan; keep humidity in EPA’s range

EPA's Brief Guide to Mold, Moisture and Your Home sets the humidity range: below 60 percent, ideally 30 to 50 percent, with the fan running during showers.

Pink mold in shower

Pink mold in shower stalls concentrates where water is last to leave: the drain, the bottom grout line, and anywhere a bottle sits in a puddle. The generic shower routine, from fans to regrouting, is on mold in shower.

Spot	Usual cause	Specific step
Drain flange and the first inch of the drain	Serratia, often with soap scum	Pull the hair catcher; scrub the flange and the catcher, not only the tub floor
Lowest grout line and corners	Serratia in the last water to dry	Scrub, then dry with a towel or squeegee; check the sealer’s cleaner rules
Silicone bead at the tray	Serratia on top, or mold in the bead	Film wipes off; spots under the skin mean replace the bead
Curtain hem and liner folds	Serratia or Rhodotorula	Wash or replace; see shower curtain mold

One conflict to resolve before scrubbing grout. NDSU advises a strong chlorine bleach solution on scrubbed surfaces, while Custom Building Products data sheet TDS-212 for Aqua Mix SameDay grout sealer (published 23 March 2023) says not to use cleaners containing ammonia, acids or bleach on sealed grout. If the grout is sealed, follow the sealer maker and use its neutral cleaner, then rely on drying.

Pink mold in toilet

Pink mold in toilet bowls forms as a band at the still waterline and under the rim, and it favours a toilet that is flushed rarely. North Dakota State University Extension links it to feces residue, a phosphorus source, and to bowl water losing its chlorine. Brush the band and the rim jets with a bowl cleaner, flush, and flush a seldom-used toilet every few days.

If pink returns quickly, the tank may be seeding it. NDSU’s tank method is 1/4 cup of bleach, 15 to 20 minutes, then several flushes, never left standing. The Kohler homeowners guide and the Fluidmaster 500 flapper instructions go further and warn against in-tank chlorine cleaners, which they say damage tank parts. The full tank routine, and black rings, are on black mold in toilet.

The method, surface by surface

Serratia is not a mold, but the cleanup logic is the same one EPA's Mold Cleanup in Your Home gives for mold on hard surfaces: scrub with detergent and water, and dry completely. The surface decides what else is allowed.

Surface	Method	Why this differs from generic advice
Acrylic or fibreglass tub and shower pan	Non-abrasive cleaner, soft brush, rinse, towel dry	Kohler prints the same warning for its fixtures: abrasives scratch or dull
Porcelain toilet bowl	Bowl cleaner and brush at waterline and rim jets; flush	Pink sits under the rim as well as at the waterline
Toilet tank	NDSU: 1/4 cup bleach, 15 to 20 minutes, flush several times	Bleach left standing harms rubber valves and seals
Sealed grout	Sealer maker’s neutral cleaner; scrub; dry	TDS-212 rules out bleach, ammonia and acids
Unsealed grout, ceramic tile	Scrub, then strong bleach solution 10 to 20 minutes per NDSU; rinse	Never mix bleach with ammonia or other cleaners (CDC)
Silicone caulk	Wipe film; replace if spots sit under the surface	A wipe cannot reach growth under the silicone skin
Vinyl cushions with pink under the skin	Not a cleaning job; replace or reupholster	PCI Magazine: no conventional way to clean pink stain

CDC caps household bleach at 1 cup per gallon of water, never mixed with ammonia or other cleaners. Bleach on true mold is covered on does bleach kill mold; label claims on mildew remover.

Is pink mold dangerous to the house?

For the building, Serratia film is a cleaning problem: it sits on glazed, sealed and plastic surfaces and brushes off. The pinks that do lasting damage are not on the surface.

PCI Magazine explains that Streptoverticillium reticulum, a bacterium of soil and decaying vegetation, feeds on plasticizer and makes a soluble red dye that is absorbed into vinyl, so growth on the back of a cushion or in its foam shows through the top. The industry test for resistance is ASTM E1428, in which specimens sit on inoculated agar for 14 days. Specifying vinyl that has passed it is the preventive step; the stain itself is a replacement item.

The Town of Blades, Delaware said extra potassium permanganate entered its system while greensand filters were tested and that the colour would not cause any harm. On a private well, persistent pink water is a filter service call.

Signs it is more than a film

What you see	What it usually means	Next step
Pink returns within a day or two of cleaning	Residue or a reservoir (tank, drain, carbon filter)	Clean the tank and drain; review the filter
Pink spots turning brown or black on caulk	Mold colonising the bead	Replace the bead
Grout stays stained after scrubbing	Growth in porous grout	Seal or regrout
Film plus a musty smell from a wall	Possible hidden mold	Investigate behind the surround
Pink under vinyl in several cushions	Pink stain spread through the foam	Replace; specify ASTM E1428
Pink tap water for days on a private well	Greensand filter overdosing or failing	Filter service

EPA's Brief Guide to Mold, Moisture and Your Home says to suspect hidden mold when a space smells moldy with nothing visible; a leaking shower can do that. Fuzzy growth larger than about 10 square feet is past EPA’s homeowner scale; the line and steps are on DIY mold remediation.

Drains are a known reservoir. Short and colleagues in the Journal of Clinical Microbiology swabbed 471 drains in 131 US buildings, more than 95 percent of them bathroom sinks, and report Fusarium in 66% of sinks. Some Fusarium species are pink, per the University of Adelaide, so a pink tint inside a drain is not proof of Serratia.

For contractors

A pink film call is a cleaning visit; calling it mold remediation overstates the scope. Billable work appears when the pink points to something else: a failed caulk bead, a surround leaking behind tile, or vinyl contents with pink stain. Record the organism as provisional unless a lab named it; mold testing covers when sampling is worth the fee.

Document	Why it belongs in the file
Photo of texture: slime, fuzz, or stain under vinyl	Separates cleaning, remediation and replacement
Water supply: municipal, well, carbon filter, greensand	Explains recurrence and pink water
Caulk and grout condition, sealed or not	Sets the cleaner (TDS-212) and the repair line
Moisture readings at the surround and floor	Rules a hidden leak in or out
Measured area of any true mold	Places it against EPA’s line

Adjusters work from policy wording. The ISO HO 00 03 sample form hosted by the Insurance Information Institute excludes “mold, fungus or wet rot” with a give-back for such loss hidden within walls, ceilings or floors from accidental discharge of a plumbing, heating, air conditioning or sprinkler system or a household appliance. A bacterial film is not named either way, so the owner’s policy, their state insurance department and a licensed professional decide.

Questions people actually ask

What is pink mold?

Usually the bacterium Serratia marcescens, not a mold. North Dakota State University Extension identifies the pink film in toilets, sinks, tiles and shower stalls as Serratia, feeding on phosphorus or fatty residue such as soap. Less often the pink is a yeast called Rhodotorula, a young mold colony, a dye inside vinyl, or potassium permanganate in the water.

What causes pink mold?

Residue plus standing water. NDSU Extension says the film grows where water sits long enough for its chlorine to dissipate, feeds on soap or feces residue, appears more during remodelling and open-window summers, and may be helped by an activated carbon filter that removes chlorine. Drying surfaces after use removes the condition it needs.

Is pink mold dangerous?

This page does not assess health effects; CDC and NIH publish that guidance, and a doctor can answer personal questions. For the house, Serratia film is a cleaning issue on hard surfaces. The pinks that cause lasting damage are pink stain inside vinyl, which PCI Magazine says cannot be conventionally cleaned, and mold inside caulk.

How do I get rid of pink mold in the shower?

Pull the drain cover and scrub the flange, the lowest grout line and the caulk with a brush and cleaner. NDSU then advises a strong bleach solution for 10 to 20 minutes and a rinse, but a grout sealer maker’s sheet rules out bleach on sealed grout. Towel or squeegee the stall dry after every shower.

Why does pink mold keep coming back in my toilet?

Bowl water stops being refreshed with chlorine between flushes, and residue feeds the film, per NDSU Extension. Brush the rim jets as well as the waterline, flush seldom-used toilets every few days, and clean the tank with a short bleach dose that is flushed out, since Kohler and Fluidmaster warn against in-tank chlorine cleaners.

Can I just use vinegar on pink mold?

No published source opened for this page gives a vinegar contact time for Serratia. NDSU Extension’s advice is scrubbing plus a chlorine bleach solution, and EPA’s general rule for hard surfaces is detergent, water and complete drying. Whatever the product, the film returns unless the surface dries between uses; vinegar itself is covered on does vinegar kill mold.