Black staining from water is typically composed of several different fungi.
Black stains caused by water don’t generally present a health risk – unless the fungal growth goes unchecked and becomes very dense.
What causes the fungi to grow?
Fungal spores are naturally present in the environment. They're airborne, which means they can be dispersed throughout buildings by air currents. When they find a suitable warm, moist location with a food source, the spores multiply and produce a grey or black ‘jelly-like’ growth.
Where is the growth most likely to appear?
- In bathrooms, where propellants from aerosols and soap residues provide a source of nutrients.
- Where there is water without chlorine. For example, around the ends of cold water taps, inside washing machines (particularly the powder draw), on shower heads and curtains, and around tiles and sealants in your bathroom. It can also appear in toilet bowls and cisterns.
- When your house has been empty for a while, fungal spores will have the chance to multiply which encourages growth.
Is my water treated for this?
Your cold mains water supply contains a small amount of chlorine, which inhibits the growth of fungal spores. However, water running through your internal plumbing system will gradually lose this protective effect.