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Drinking water quality

Biofilms – Slime and Staining

What is a biofilm?

A biofilm is a layer of biological material that can consist of a mixture of bacteria, fungi and protozoa which are naturally present in the household environment. In order to multiply, these microorganisms require water and a source of nutrients.

Where can biofilms occur?

Biofilms can grow on any surface that is regularly in contact with water, and such areas are usually in the kitchen or the bathroom, for example:-

  • shower heads and curtains
  • kitchen and bathroom tiles
  • toilet cisterns and bowls
  • drains and plugholes
  • inside washing machines, particularly around the powder drawer and rubber door seal
  • on the inside of cold water taps, especially those with plastic inserts
  • around the base of tap fittings
  • refrigerator drip trays

Are biofilms harmful?

Although they can appear unpleasant, biofilms are generally not considered to be a risk to health.

How can I prevent / remove biofilm growth?

There is nothing that we can do to the drinking water supply to prevent the growth of biofilms within customers’ properties. However, some steps that you can take to prevent biofilms are:

  • Improve ventilation to allow damp areas in kitchens and bathrooms to dry quickly
  • Reduce the amount of food/nutrients available for bacteria and fungi e.g. shampoo, soap, washing powder, dust, general kitchen food etc.
  • Ensure any water filters or softeners are serviced according to manufacturer’s instructions.
  • Make sure that the storage tank that supplies showers and internal plumbing is covered and free of debris.

Biofilm growth can be removed from kitchen and bathroom surfaces by cleaning with a mild bleach solution or other household cleaner. Any growth on the inside of taps can be removed by cleaning with a small brush dipped in a mild bleach solution. The tap should then be flushed afterwards by allowing it to run for a few minutes. 

Please click here to read our Biofilm Factsheet 

Please contact us on Waterline: 0345 744 0088 for if you require further information or advice.

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