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09 May 2012

My tap water tastes odd

Water Affairs assures us our tap water is excellent and stringently tested, so why does it sometimes look cloudy or brownish, or taste or smell peculiar?

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Water Affairs assures us our tap water is excellent and stringently tested, so why does it sometimes look cloudy or brownish, or taste or smell peculiar?

South Africa's tap water is considered to be of world-class quality, at least if you live in one of the bigger metropolitan areas. (There is less confidence about water quality in some of our smaller towns: see this recently released list of places where tap-water is below standard.)

Occasional variations in how water looks, tastes or smells are usually no cause for alarm. Still, it's good to know when a change may be harmful and warrants reporting to your local water authority. And besides, as the World Health Organisation puts it, being “pleasant to drink” is an important attribute of tap water quality.

Some common tap water problems:

My tap water has an earthy taste and smell

Some Cape Town residents have noticed this recently. The cause is usually a substance called geosmin, which is sometimes produced by algae in water bodies, usually in summer. See City of Cape Town's explanation.

Should I be concerned?

No. If the smell and taste persist longer than a few weeks however, report it.

My tap water has a “swimming pool” smell

This is caused by chlorine which is added to drinking water as a disinfectant; it's highly effective in killing disease-causing micro-organisms.

Should I be concerned?

No. This small amount isn't considered dangerous to health.

My tap water smells of rotten eggs

This distinctive smell is probably due to the gas hydrogen sulphide. Sulphur-producing substances are produced by certain bacteria and fungi in water bodies, as well as bacteria sometimes found in water pipes.

Should I be concerned?

Our sense of smell can pick up very low levels of hydrogen sulphide; a faint rotten-egg whiff doesn't indicate harmful levels. 

But high levels are toxic. If there's a sudden strong sulphorous smell, turn off the tap and get outside into fresh air. Report it at once.

My tap water has a mineral taste

A salty or metallic taste can be caused by various dissolved mineral salts. These come from rock, soil and vegetation the water passes over. Some enter drinking water during treatment.

Should I be concerned?

Some minerals are vital for health, and drinking water is a good source: lack of key minerals can cause deficiency diseases.

However, excessive amounts of certain minerals, even those beneficial at low doses, can be toxic. If you notice a sudden change in taste that persists, it's worth reporting. But keep in mind that levels of minerals in drinking water vary naturally in different areas, and can cause considerable variation in taste.

My tap water looks cloudy/milky

Fill a glass from the tap. If the “milkiness” clears from the bottom up, it's caused by tiny air bubbles.

If the water clears from the top down and a white substance settles on the bottom, there may be an excessive mineral or chemical concentration.

Should I be concerned?

Air bubbles in water are harmless; if you don't like them, opening the tap more gradually usually reduces the problem.

Formation of sediment shouldn't happen in well-regulated water, and some of the chemicals causing this may be harmful. Report it.

My tap water looks reddish-brown and tastes metallic

Rust

Your geyser or water pipes may be rusting. Rust can form in the pipes when water isn't being used for a while, and then gets flushed out when you open the tap.

Rust is iron oxide, and may also be dissolved in the water. When it's exposed to air it turns reddish-brown, and gives the water a metallic taste.

Should I be concerned?

Iron is an essential nutrient and is safe at the low levels normally found in drinking water.

High iron levels can be toxic if consumed over many years, however. Young children are also susceptible to acute iron poisoning.

If it's only your water that is “rusty”, and not other households in your area, call a plumber. If the problem is more widespread, or your plumbing is in good order, then report the problem to your local water authority.

Tannins and other organic compounds

Organic compounds leach into water as it flows over certain kinds of vegetation, lending water a brownish tint. This occurs typically in the Western and Eastern Cape, where tannins in the fynbos vegetation give rivers a rich “brandy” or "cola" colour.

Should I be concerned?

No, this is completely harmless.

My tap water has...worms!?

These are most likely to be insect larvae called Chironimids: thin pinkish-red “wormlike” midge larvae (the adult midge looks like a small fly or mosquito).

Should I be concerned?

No. The larvae are harmless, even if you swallow one. But you shouldn't have to put up with them either – report them.

- Olivia Rose-Innes, EnviroHealth Editor, Health24, May 2012

 
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