Help & Advice

What causes stains, slime or mould?

Customers sometimes notice a build-up of slime or staining on fixtures and fittings in areas where water is present.

Common problems include black mould on taps or black, red or pink staining to tile grouts or shower curtains.

While this can raise concerns about the quality of water these problems are not connected with the mains water supply.

How does staining occur?

Bacteria and fungi exist naturally in the air and remain invisible to the human eye.

However, they grow quickly and become more visible in warm, moist environments especially when they have a source of nutrients. Typical forms of nutrients include shampoo, soap, spray from aerosols, washing powder, household dust and food. This visible black slime or staining is called a biofilm.

Where do they form?

Bathrooms and kitchen are ideal places for biofilms to grow.  They will form more readily on rough surfaces, such as limescale.

Common places include the inside of cold taps where they can form a slimy or jelly like deposit which hangs from the end of the tap.

They can also be found:

  • Around the base of tap fittings
  • In showerheads or on shower curtains
  • On tile grout
  • In drains or plugholes
  • In toilet cisterns or bowels
  • In washing machines, particularly around the powder draw or door rim
  • In refrigerator drip trays or ice making machines
  • In drinks vending machines
  • In dehumidifiers

Click here to find out how to remove and prevent biofilms

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