A coupler is described that precludes fluid communication between the first and second pipes attached on either side of the coupler. The coupler may be used in installations where a line branches off from a sewer main for future connection to a home or other building. The coupler includes a barrier wall located between first and second portions of the coupler, and the barrier wall precludes fluid communication between the first and second ends of the coupler. Moreover, the second portion defines an area of weakness that is designed to fail (e.g., flex or crack) when a failure force is applied near the second end, such as when an exposed (above-ground) portion of piping connected to the coupler is struck. In this way, the barrier wall and the first portion of the main wall can remain intact and continue to protect against entry of fluids into the sewer system.