schedule 40 pvc pipe slip x slip coupling (1 1/4" dia. (5 pack)) - 429-012 maxx flex slip coupling for schedule 40 pvc pipe (slip x slip). if you are just making a connection or repair and do not foresee the need to take the connection apart in the future, the easiest way to connect two pieces of pipe of the same size is with a slip coupling. slip couplings are used when the pipe doesn’t need to be taken apart and you are simply joining two smooth pipe ends together. both pipe ends are glued into the coupling, forming a joint. all of our schedule 40 fittings are nsf rated 14 & 61, which means they are certified for use with potable (drinking) water. maximum temperature is 140 degrees f.