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Black & pink slime

• What is the black or pink slime I see in my kitchen or bathroom?
• The staining or slime which can accumulate on kitchen and bathroom tiles is quite common and is due to the presence of airborne mould, yeasts and bacteria, which grow in damp areas. Their presence does not indicate a problem with the quality of the water and they are generally harmless.

• Why does this slime or staining occur and how does it grow?
• The slime, or biofilm as it is also known, can thrive in moist warm environments, like those found in bathrooms. The problem is more widespread when there is poor ventilation, or if shampoo, aerosols, deodorants or other sprays or food are used as these provide a food source for the airborne moulds, yeasts and bacteria.

• How can I prevent fungal growth occurring?
• By simply improving the ventilation in the room by opening a window or fitting an extraction fan. Replacing rubber washers on taps with ones made from other materials may also help, as rubber can encourage growth of biofilms. Organisms may also grow more quickly on rough surfaces, for example where there is limescale, so cleaning off limescale either with sodium bicarbonate solution or proprietary cleaning materials should help.

• How can I get rid of the slime or staining?
• Clean tiles or flat surfaces with bleach solution or household cleaners and clean around taps using a small brush (an old toothbrush is ideal) dipped in mild bleach solution.

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