These are the three most common mistakes I run into when I am doing a service call and repair. I run into these things all the time and I don't mind fixing them, but most of these mistakes could have been avoided if things where done right to begin with. Number one, a leak in a sprinkler system caused by fittings and pipes not glued ( solvent welded) properly. Number two, I find the wrong nozzles installed in the wrong places. Number three, I find a controller not programmed right. All these mistakes can be avoided if we learn how to do it right and take the time to do it right and do it right the first time. These mistakes can cause the sprinkler system to not work and or not work at all. It can cause you to waste a lot of water. And it can cause the landscaping to look bad. It is important that we take the proper steps and procedures to correct these mistakes and get these things right.