Why, it's such an innocuous little photo. A few copper pipes mounted in a wall. I too once shared this naivety, until the events of last Friday. (Why do work disasters always happen on Friday?)
Let's be clear. When I parenthetically refer to "disaster", I'm exaggerating, or being sloppy, or both. "Narrowly Averted Catastrophe" would be far more apt.
The plumbers finished their Rough In on Friday, which means they brought the water, drain and vent lines to where the fixtures will eventually be placed. They do that, then the walls and floors are sheathed with just the rough ends of pipe sticking out. When everything is just about finished and the fixtures and finishes are in place, they return and hook it all up. That stub you see above will eventually feed hot water to a tub/shower. When the pipes are in place and capped, the plumbers turn the water mains back on, then open all the valves in the room to make sure there are no leaks, then turn the room valves off, the main valves, of course, needing to be open to provide the rest of the home with water.
Oh wait, did I say they turn the room valves off? I meant, they almost always turn the room valves off. Even if they don't, it's usually no problem, as they've checked for leaks already. It's really just a safeguard.
Now lets go back and look at the picture. Look at it carefully. What makes one joint look different than all the others? If you said "The top joint on the left doesn't have any silvery stuff on it" you win. That silvery stuff is solder, and that solder is what seals and connects the pipes and fittings. Of course, the preparatory goop they put on the pipes and fittings and the snugness of their fit could, say, keep water at bay for...oh...the length of a quick leak test, but without solder, they are not connected in any real way.
So there we are, working away in the afternoon, the plumbers long gone, when Carl spots a small damp spot beneath that area of the fittings. This is not a huge deal, probably a solder joint has a small pinhole leak. It's the sort of thing you need to investigate, however, so he kneels down to get a closer look...
Now, I don't know what kind of life Carl is living, but it must be pretty much on the straight and narrow, because I'm pretty sure it isn't my Karma that caused that joint to blow open at the exact moment he came over to check it out instead of, say...midnight. Did I mention the homeowners were away?
For some reason, that full-bore complete failure happened exactly as his hand approached the fitting. If this doesn't seem like a big deal, bring your garden hose into the middle of an upstairs bedroom then open the spigot on your way out of town for the weekend.
Turns out, the plumbers missed the solder joint and left the room valves turned on. As time went on, the pressure in the pipe kept pushing that unsoldered joint farther and farther down. Karl saw it just before the fitting cleared the final bit of pipe.
Did I mention it was the hot water feed? The room valves turned out to be oddballs, which was why the plumbers made their mistake. They turned them in the direction that should have been off. This means that when I ran over to turn them off, they were indeed in "off" position but the water kept flowing and getting warmer and warmer, as your own experience will reinforce. This led to much running up and down by me from this third floor apartment to the building basement to find and close the building mains before the water got too hot for Karl to keep his finger in the pipe.
In retrospect, hilarious. And overall, really, really damn lucky.
This is why I like going to work.