I have a 3 yr new construction house with grinder pump in basement.after 2-3 washing machine uses,the smell appears in the basement.. its a ranch style home with all p traps installed and 3 roof vent s... smell does not appear to be coming from pump itself,but is contained to the 1/4th basement area only where 75% of drainage occurs.. had thoughts of installing a line fan in the main grinder pump vent in the attic.. there is a vent for the wahing machines... any thoughts out there... george

So there's a vent for the washer, is there a trap for its drain or just a stand pipe?