The answer seems fairly obvious, but maybe I am wrong. Many water heaters have extension pipes plumbed into the pressure relief valves. I'm assuming that this is to keep hot water from spraying around if the valve opens:
On the water heater in my garage, the pipe runs to a little bit above the floor and then ends. This seems like the normal correct way to do this. At my uncle's house, however, I noticed that the plumber soldered a cap on the end of the extension pipe. This seems not only wrong, but potentially dangerous as the valve will simply open into a closed pipe which has no way to actually relieve the pressure of the valve it was installed for in the first place. Is this as wrong as it seems, or a completely normal installation?