Squeezing pipe has never been able to offer a 100% leak free shut off. 100% means, to us, that there will never be a bubble of gas escape ever. That is not possible. A 95%-98% shut off should be attainable in most cases. Some pipe produced in the last several years has proven to be more difficult to squeeze than some of the older material. If after squeezing all the way to the gap stops, the flow is still not controlled, it may be necessary to install a second tool on the line.