Purpose
This information sheet sets out the potential
causes of a consumer's concerns with the aesthetics of their
drinking water, for example, in terms of colour, taste or
cloudiness.
If a consumer believes there is
something wrong with the drinking water in their home or workplace
they should contact their water company, or in the case of private
supplies, their local authority environmental health
department.
Context
Water from the tap, whether from public or private supplies,
should be not only chemically and microbiologically safe but also
meet certain aesthetic (i.e. not health-related) water quality
standards which are discussed briefly below. A noticeable change in
these aesthetic parameters may also be an indicator of a change in
the safety of the water to drink, although water that is free of
these aesthetic problems is not necessarily safe to drink.
Aesthetic Parameters
Tastes and odours may be caused by a
range of organic substances such as algal products (e.g. geosmin or
2-methylisoborneol, imparting an earthy or musty odour) and
inorganic substances including copper, zinc, iron, manganese
(imparting metallic tastes) or chloride (salty taste). Tastes and
odours are somewhat subjective; some people are more sensitive, and
when people travel to other areas they often notice that tap waters
taste differently than their normal sources. Many of the chemical
substances that cause tastes and odours are regulated with maximum
concentration levels which have been set to reduce the effects to
below what most people will notice.
Colour may indicate the presence of
metals such as iron (imparting a rusty colour), manganese
(imparting a black or brown colour), or copper (blue and green), or
dissolved organic matter. Colour changes at the tap are more
commonly associated with effects occurring within the water
distribution network (e.g. re-introduction of flow following an
interruption) rather than problems at the water treatment
works.
Turbidity is
a measure of the cloudiness of the water, caused by small suspended
solids in the water. As with colour, this is more commonly
associated with disturbances occurring in water distribution
networks, such as re-suspension of sediment in water mains due to
hydraulic pressure transients. Sometimes entrained fine air bubbles
cause a temporary cloudiness in the water and this disappears on
standing.
Scale is a mineral
deposit which builds up on the inside of household appliances such
as boilers, water heaters, kettles and in hot water pipes, which
can restrict or even blocking flow over time. While water companies
must ensure that tap water falls within certain ranges of hardness
and total dissolved solids, in some locations water softeners may
still be recommended to minimise scaling effects.
Corrosivity, for example due to low
water pH, can lead to corrosion of iron and copper in pipes and may
thereby lead to staining of household fixtures and impart tastes,
odours, and colours to the water.
October 2012
Further Information
The following websites provide further useful information about
these and other aesthetic water quality issues, their causes, and
correction measures:
