These days we are upgrading lead water mains to copper more than other reason. Historically we had been replacing water mains most commonly as a result of a leak, until all of the recent conversations about lead poison. Over previous years the government has become increasingly concerned about traces of lead in water after continuous studies prove there is a huge health risk.
Most recently there have been thousands of children testing positive for lead poison. The positive tests were not necessarily a large concern however, experts are not aware of the long term risks associated with low levels of lead in water. For this reason most property owners avoid all risks and upgrade their lead water mains with copper.
In NYC we have been installing copper water mains for more than 50 years with no negative side effects. In addition, the average life span of a copper water main is 60-70 years which surpasses that of old lead water mains.
If you are not sure of the material make up for your water main it is important to speak with a licensed plumber who can assist in understanding your potential risk, as well as the process if you are looking to install a copper water main.