What is the proper plumbing test pressure and for what duration. I ask because I tested my two skimmers at around 20 psi and the skimmer extension (the female fitting where my piping attaches to) has developed hairline cracks on each skimmer. I will need to pull out each skimmer and replace/re-pipe. The piping that I installed is fine. Is it normal to test the skimmer piping as I did?