Much of the system was built in the 1930s and 1940s. Those pipes are 80 years old. This means that they held up for 80 years without incident. This alone shows how incredibly safe Natural Gas is. Only waterpipes hold up longer. My suggestion – replace everything every 40 years or so. That’s still very long for amortizing those pipes and you are on the super safe side.
The recent natural gas pipeline explosion in Massachusetts showed that many of our oil and gas pipelines are aged. In fact, much of the country’s natural gas pipeline system was constructed in the 1930s and 1940s, susceptible to rust and corrosion, which can lead to leaks and explosions. There is a national necessity not only to build more pipelines but also to replace the old ones.