Odor coming from shower drain
We’ve lived in our new house for one month. There is a pungent broccoli and dirty sock odor coming from one of the three bathrooms. Prior to moving in, the plumber dug up the slab to add a shower and moved the drain for the tub. This is a one-story and all drains in the bath are going to the same roof vent. To eliminate the odor, the plumber dug up the new shower drain and added a “P” trap. The plumber ran cold water down the drain to keep the “P” trap moist. The next day, the septic tank was inspected, pumped and cleaned. There is no blockage from any of the drains and the drain field is not a problem. The smell went away for a couple of days. Then after I washed two loads of laundry, the smell was back. We have not used the shower due to the odor. The odor is not continuous and only smells after I use the washing machine. Can anyone help me with this problem?