Although lead-based paint and dust in older buildings are the most common sources of lead poisoning, drinking water is sometimes a source as well. This is mostly due to old, corroded pipes.
Since you can’t see, smell or taste lead in water, the only way to detect it is to have the water tested. If your home is served by public water systems, your local water authority should be able to provide this information. You can also use an at-home lead-testing kit.