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

It's not usual to install a washer trap under the cement. Your plumber installed the trap under the cement because that gave him a clear shot at the main. Your fears are valid. The washer has been installed without a vent. Have you paid him yet? Good luck, Tom

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 dont 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 didnot pull a permit.

thanks
No, I havenot paid him yet. What do he need to do to the current setup to vent the washer(my major concern)?

Thanks

He needs to roll a fitting up on a 45 degree angle after the "P" trap and run a vent up to the attic and revent into a existing roof vent or if he can get to a dry vent before the attic revent back into it at least 6 inches over the flood rim of the fixture the vent services.
Or he could come off the main and keep the trap above the floor band extend up for a re vent. I've made a rough freehand drawing,(see image) for a guide.
Good luck, Tom