Some plumbing materials that come into contact with the water supply in homes, offices and factories can give water unpleasant tastes and odours.
When water stays in contact with plastic or rubber pipes or fittings, small amounts of substances may dissolve into the water. Traces of chemicals routinely used in the manufacture of flexible plastic hoses, usually ones which supply cold water to dishwashers or washing machines, can interact with chlorine to create an antiseptic or TCP-type taste. When the drinking water tap is turned on a small amount of the water lying in these hoses can be drawn back into the cold supply. This problem usually occurs when the hose is connected directly to the rising main.
To check whether these hoses are causing the taste, close the isolating valve for 24 hours and then check the taste again.
You could also change the hoses for those approved by WRAS (Water Regulations Advisory Scheme), for example a food-quality hose, or change the isolating valve for one fitted with a check valve.
This type of taste can also be caused by a having a garden hose permanently connected to an outside tap.
You should remove hoses from the tap when they are not in use and install a double check valve between the tap and the hose. A qualified plumber will be able to offer advice on how to do this.
As with all fixtures and fittings, plumbing materials deteriorate over time. Very old washers can begin to disintegrate or become damaged, for example by a worn tap seating, and this can change the taste of your water. The most commonly affected areas are the kitchen tap and the stop tap.
Try replacing old and worn out washers and or tap seats - this will help improve the taste.
Drinking water with this taste, although unpleasant, is not harmful in itself.
If you've tried this but are still concerned, or you'd like more advice you should contact your water supplier.