If your house was built before 1970 then it’s worth checking what your pipe are made of in a few places. The best places to inspect are generally under the kitchen sink and at the internal stop tap (if this isn't under the sink, it may be in the downstairs loo or in the garage).
Once you've found the stop tap, you'll need to find out what the pipe coming in to it is made of.
Lead is a very soft metal, irregular in shape and scratching the surface is easy and will leave shiny marks.
Tapping a lead pipe with a coin will produce a dull noise rather than the metallic ringing of a copper pipe.