PVC Pipe

There are a few more tricks. If you need to glue two PVC pipes 3" and 4"
together, but you do not have reduce coupling, and you have 3 " coupling only. What you have to do ? You have to stick up 3" coupling and 3" Pipe as usual. And same 3" coupling stick inside 4" Pipe. Because the outside diameter of 3" coupling exactly 4", v.e. inside diameter of 4" pipe. All very simple.