TCP or medicinal type tastes can be caused by a number of sources within the home. Chlorine is the most common form of disinfection across water companies. Chemical reactions between chlorine and certain fixtures and fittings can result in phenolic chemical compounds being created. In extremely low levels these compounds are not considered harmful but can lead to noticeable tastes and odours of TCP (antiseptic) or medicinal. If you notice a particularly bad or strong smell or taste which means you cannot drink the water, or you notice a smell or taste for the first time you should contact your water company immediately.
What could be causing the taste and odour?
If the taste or odour is only present in hot drinks or boiled water and is not noticeable in freshly drawn cold water from the kitchen tap this could indicate the problem lies within your kettle. To confirm this try boiling some water in a saucepan instead. If there is no smell or taste the kettle is the likely cause. Kettles contain rubber seals and other plastic parts which may be reacting with chlorine. The issue is more common in new plastic kettles and the problem may go away over time, as you use the kettle. Always follow manufacturer’s instructions when using a new kettle for the first time.
Appliances (such as washing machines or dishwashers)
Most modern dishwashers and washing machines are connected directly to the incoming mains water supply but are sometimes not installed correctly. All connections should include a non-return valve so that water standing in the hoses does not get drawn back into your drinking water. If the appliance does not have a non-return valve it is possible to get a rubber, plastic, disinfectant or TCP taste and odour in your tap water. To test if an appliance is the problem turn off the water to the individual appliance using the service valve. Run the tap for a while and if the taste and odour are no longer present this indicates the source of the problem was the appliance.
It is also possible that your tap washer or some part of the tap is the cause, especially if you have recently installed new taps. If you’re getting an unusual taste or smell from your kitchen tap, try using another tap in the house, such as the bathroom sink, to see if the different taste or smell is also present there. Alternatively run the original tap for a few minutes before tasting the water again. This may clear the problem through flushing. If the taste or smell persists then it could be caused by a washer or fitting in the stop tap.