What flooded my basement?

Question

The other day I came home to a collapsed ceiling and about an inch of water in my basement. Just before leaving the house we did a load of laundry and flushed the toilet. The toilet on the first floor had sand in it. There was a little water on the floor and outside in my family room. The washing machine is located right next to the bathroom, and drains out a pipe into my yard. There is no indication exactly where the water came from. I'm stumped When cleaning up the water, it was sudsy. But have done a load since then as well as flush toilet.Still no idea what happened.Washing machine drain appears intact and working as does toilet. Washing machine drain hose sits in top of drain pipe, maybe backed up somehow. dont know.Cant understand if either washing machine or toilet overflowed why I have ALL water in basement and hardly any on first floor? Amount of water in basement indicates that pipe in ceiling was problem,but thats not the case. Any help or theories would help. Thank you

Answer 1

Sir Sherlock noted that the water was sudsy and concluded that unless you have been eating soap, it was probably from the washing machine, not the toilet.  The toilet had been filled with sand (Who has been eating sand?  If not a dietetic filler, why was it in the toilet?) and the DWV was clogged and restricted the flow of water.  The washing machine drain apparently flows into the main soil pipe (DWV) above the blockage, and flowed back out of the top of the washing machine drain and flooded the floor.  Gravity allowed the overflow to drain to the lowest level at the floor, which was not watertight and thus drained through the floor to the ceiling below.  The ceiling became supersaturated and gave way collapsing to the floor and the water drained into the basement.  The water rushing through the DWV loosened the sand enough to flush the blockage down the drain.  So when you returned home anticipating the laundry you had left running would now be complete, you discovered this huge mess created by all the water a normal wash cycle uses.  

In a variation, assuming that the drain was in no way connected to the DWV and poured through a hole into the yard, the ground became saturated and flowed back to the foundation and leaked to the inside.  However, this would not have allowed all the water to leak into the basement, so the water in the basement seems a bit much.  Also, this would have been below the ceiling line, so the ceiling would not have collapsed.  The water obviously went through the floor.

It was elementary, my dear Mr. Watson.  

(Think I'll use this one at our next Mystery Night Dinner theatre.)

And the moral is don't leave with the water running.