Open Plumbing Waste Pipes
Anytime you run into a situation like
this where the plumbing pipes are disconnected, mark the location in the
crawl space in your mind, try to get a good idea where you think it
would be located in the floor above.
This pipe was an old toilet that was never replaced but the pipe was disconnected for some reason.
The biggest problem with a situation like this, would be when or if the drain ever clogged. If the drain was to clog with an open waste pipe like this, the sewage could actually start draining into the crawl space area.
If you rarely check the crawl space, it could be flooding for days, if not weeks, without you ever knowing.
It wouldn't take much to solve a problem like this.You can go down to your local home improvement center and purchase a plastic cap or plug to glue on to the end of the pipe or pick up a rubber cap that could be easily attached using a screwdriver.
You should never leave an open waste pipe anywhere. The biggest problem with open pipes would be the horrible smells coming from them, these smells would of course make you cover the pipe up somehow.
You could also have problems with people dropping items into them and eventually these items would work their way down to a spot that could cause the drain to become plugged.