I'm having some plumbling work done(adding washer to half bath). The plumber can out and connected a drain to the main line for the washer. The problem I don't understand why he installed a P-trap under the floor which is to be filled in with concrete later. I also concerned on how he will vent the washer. Most setup I see the P-trap is aleast 6in off the floor. By the way, the plumber did not pull a permit.
Thanks