Source - Water UK Consumer's Guide
Lead Contamination of Drinking Water
There is no lead in water when it leaves the water treatment works. However lead can be picked
up by the water if the service pipe (the pipe connecting your property to the main in the street),
is made of lead. Lead can also be picked up from any internal lead pipework and lead-based
soldered pipe joints inside your home.
If your home was built before 1970 it may have lead pipes. If it was built after 1970 it is unlikely to
have lead pipes.
Other Issues Affecting Drinking Water
It is important that taps that are used for drinking water are kept clean. Whilst the water coming
to your tap is safe, many bacteria can live in the kitchen and some can grow both on the outside
of the tap and inside the lip of the spout.
Ideally you should only use a mains fed tap for drinking water. However if your drinking water, or water for brushing your teeth, comes from a storage tank, you should check the following:
Is your tank in good condition?
Nowadays, tanks are constructed of plastic (polyethylene) and are unlikely to cause problems
provided that they are designed for drinking water purposes and have a closely fitting cover.
Is the tank covered?
Ensure your tank has a close-fitting lid of a suitable material that will not deteriorate or allow
mould or bacteria to grow on it and drip into the water. The lid must prevent debris falling in and
polluting the water supply. It is not uncommon for birds, rodents or insects to find their way into
tanks that are uncovered or only partially covered.