Methods of sealing annular space between inner and outer gas mains for tie-overs

In a method of tying over an individual customer service connection from a live outer gas main to an inner gas main inserted within the live outer gas main comprising the steps of defining a generally annular region within the space between the inner and outer mains, said region being upstream from the customer service connection between the customer service connection and the source of gas for the outer main, opening a sidewall of the outer main intermediate the ends of said region, introducing into said opening an amount of a high-density liquid foaming composition sufficient to fill said region, permitting the foaming composition to foam and harden to a plug in said region, removing a section of outer main downstream from said region, and placing the new customer service connection through the sidewall of the inner main exposed by cutting away the outer main, the improvement comprising, before permitting the foaming composition to foam and harden, inserting into said opening a first end of a first conduit having said first end and a second end, and pushing said first conduit into the space so that said first end lies upstream of the region so that said first end of said first conduit will not be obstructed by said hardening of said foaming composition.