Water in the house - AGAIN

This is the house that Jack built.
Jack must have been thirteen and experimenting with lego toys.
THis house is doesn't just leak now and then, it explodes.
The drain pipe from the kitchen sink runs down through the basement wall in the new MAN CAVE room. Remember that one? We just finished remodeling it.
When we built the first two walls back in 2003 a neighbor had me cut an access route through the drywall to the cap on the drain. Good thinking. Until now I never thought a thing about that opening.

Yesterday morning, I ran downstairs to the storage room for something. The first clue that something was wrong was the wet socks on my feet as I ran into the MAN CAVE. Then the 1/4 inch of water on the storage room floor made me scream.
I turned around to the water softner setup and thought it must be coming from there. The night before we had received a blast of salty water from the daggum thing. I immediately called the company that had installed it. I would have to wait until the afternoon for someone to come look at it, so I was instructed in how to turn it off. As I started to mop up the floor, I realized the water didn't come from there it was coming out of the carpet from the MAN CAVE. I went back around the door and found the corner sopping wet. I moved the filing cabinets, and saw the access panel. I did not have a good feeling about this now.  I clawed the molding off, and opened the panel to find the cap from the drain pipe complete off and leaning on the stud. The bloody cap had blown off emptying the dishwasher water into the room. I called the company back. They could get the plumber out here about the same time as the water softner guy.

I don't know how many times I've heard a plumber say this about this house - "They don't do it like that anymore. THey quit doing that fifteen years ago because it doesn't work." We keep finding those kind of things out with this house. The pipe has been fixed, the carpets pulled back, fans running. The MAN CAVE carpet and the tv room carpet both got doused.
Let's see.... there has been the bathroom upstairs,the outside water faucets,  the bathroom downstairs, the kitchen drain.... ewwww, that leaves the master bathroom as the only one still to have a major blowout.