On Saturday, 1 February 2020 22:36:54 UTC, Steve Walker wrote:

When they replace the main, they can run at a higher pressure (having
eliminated potentially leaky joints), so the run to the house can be a
smaller diameter and still achieve the same gas flow. They normally push
a new, plastic pipe through the existing metal one.

SteveW

A few years back we had a mains water leak, which revealed multiple gas leaks. The combiantion ended up with them (gas and water - and me) digging up half our garden. The water leak had already turned most of the garden into mud...