Why does my tap water taste of chlorine (or TCP)?

Taste is the most common reason people stop drinking water straight from the tap. A hint of swimming pool, a medicinal note in your tea or an earthy smell in summer can be off-putting — even when the water is perfectly safe. The good news is that most of these tastes have a well-understood cause, and many can be fixed at home.

Chlorine: the “swimming pool” taste

Water companies add a small amount of chlorine to drinking water. The Drinking Water Inspectorate (DWI) explains that water is already safe when it leaves the treatment works; the trace of chlorine is there to keep it that way as it travels through miles of pipes to your tap.

The amounts are small. The World Health Organization's guideline maximum for chlorine in drinking water is 5 mg/l, while the DWI says most UK water companies keep levels below 1 mg/l. At these levels chlorine is, in the DWI's words, a proven public health measure and perfectly safe to drink.

Some people are simply more sensitive to the taste than others. You may also notice it more if you live close to a treatment works, or occasionally after maintenance work in your area.

How to reduce the chlorine taste

• Use the fridge. The DWI's simplest tip is to put a jug of tap water in the fridge for a short while — this reduces the chlorine smell and taste. Cover the jug and throw away any water left after 24 hours.

• Use an activated carbon filter. Carbon is very effective at reducing chlorine. Filter jugs, tap filters and under-sink systems all use it — see what different filters remove. Follow the maintenance instructions carefully, because an old cartridge can harbour bacteria.

TCP, antiseptic or medicinal tastes

A taste like TCP or antiseptic, often most noticeable in hot drinks, is usually caused by a reaction between the chlorine in the water and certain rubber or plastic parts in your home — commonly kettle components or the hoses and washers that connect washing machines and dishwashers to the plumbing. The DWI says this taste is not harmful at the levels usually found in tap water.

How to track it down:

• Taste cold water from the kitchen tap. If it tastes normal, but boiled water does not, the kettle is the likely culprit.

• Check whether the taste is in all taps or only the kitchen tap. If it is only the kitchen, appliance hoses connected near it are a common cause. Fitting a non-return valve or replacing the hose, done by a plumber, often solves it.

Metallic or bitter tastes

The DWI links metallic or bitter tastes to water in contact with copper, iron or galvanised pipes. The taste tends to be stronger when the water has been standing in the pipes, or when it is warm. Running the cold tap for a short while before use usually helps. Always drink and cook with water from the cold tap, not the hot.

If you live in an older house, a metallic taste is also a good reason to check what your pipes are made of — read our guide on lead pipes in older homes.

Earthy or musty tastes

An earthy or musty taste is often caused by water standing unused in pipes, for example after a holiday or in a rarely used tap. The DWI says it is caused by harmless, naturally occurring bacteria or fungi. Run the tap to flush out the stale water.

It can also be seasonal. Around half of the UK's drinking water comes from rivers and reservoirs, and in summer natural processes such as algae growth in reservoirs can give water an earthy taste.

Plastic or rubbery tastes

These usually come from unsuitable plumbing materials — hoses, pipes or fittings that are not approved for drinking water. The DWI recommends using a plumber registered with an approved scheme such as WaterSafe for any work on your plumbing.

When to contact your water company

Before calling, do a quick check:

• Does the taste come from every tap, or just one?

• Is it in cold water from the kitchen tap, or only after boiling?

• Do your neighbours notice the same thing?

If the taste is in all your taps and your neighbours have it too, the cause is likely in the public supply — contact your water company and describe the taste as precisely as you can. If it is only in your home, the cause is more likely to be your plumbing or appliances.

The short version

A slight chlorine taste is normal and safe; a covered jug in the fridge or a carbon filter will take the edge off it. Antiseptic tastes usually point to the kettle or appliance hoses, musty tastes to water standing in the pipes. If you also see scale in the kettle, our guide to hard water and limescale may help too.