The reaction of natural organic compounds with chlorine when the water is boiled, or in new houses that have plastic pipes may cause a plastic taste.
What to do
If your water has a plastic taste after boiling try using a stainless steel kettle, use fresh water each time you boil the kettle, allow water to stand in the sunlight in a covered glass container for 2 hours, and/or add freshly squeezed lemon juice before boiling.
If you are in a new house with plastic pipes, run the tap for 30 seconds to flush water from the pipework. Be sure to collect this water and use it to water your garden or pot plants.