You will probably have trouble figuring out the photo below. It is not a loose plumbing supply pipe. This is something a home inspector sees over and over again. The drain from the temperature pressure relief valve from the hot water heater is routed to drain under the house into the crawl space. There are a couple problems here (1) it is contrary to plumbing guidelines which state that the TPR drain should be visible, just in case the TPR valve develops a leak because you want to know there is a problem (2) should the TPR valve develop a leak, or if there is an occasional discharge, then that water will end up in the crawl space. And, as you know, water in the crawl space is to be discouraged. In this state this is labeled as a conducive condition for attracting wood destroying organisms such as termites, carpenter ants, wood decay fungi and anobiid beetles. A plumber should be contacted to route the line outside the crawl space to a visible location.
Thank you for stopping by.
Steven L. Smith