Cold water supply to washer has straight release to drain. Why?

[Tobias]

I am wondering about some plumbing for my Bosch washer and dryer. Does anyone know why there is a hose coming of the cold water pipe that goes straight to the drain? See attached photo 2 thirds down. A few days ago it just has water running non stop even with the washer turned off and unplugged. The washer is working fine otherwise.

 

[Matt30]

Trap seal primer.

It's there to keep the trap of the floor drain full of water to keep sewer gasses from entering your home.

If it's running constant, it has now failed. They operate on pressure differentials when your washer takes on water. Contact a plumber to have it replaced.