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:
