I use the both the 1 1/2 inch 90 degree Elbows, the straight connectors, and the 90 Degree Qwik Tees for connecting the PVC pipes on my KOI pond. I have had to redesign the configuration of my filters and pump a number of times and these connectors are much more forgiving than PVC when it is glued. I would have had to take out all the PVC and start over again without them. It is also helpful to use one of the straight rubber connectors on both sides of each value. That way you can take the value out if necessary to clean them.