Sewage smell in bathroom

[Borrego]

Well a few years ago I plumbed my own bathroom addition................that space is for the laughter.....
I'm a GC and have done a lot of plumbing so I thought I'd be fine but apparently I screwed something up. Would appreciate some help from you wise people.....I've attached a rough drawing, hope that helps...

The odor comes and goes, it can be gone for a couple weeks and then one morning while brushing your teeth, there will be a strong odor from the sink next to you, or from the shower... I run water to fill up the traps and turn on the fan, but this is getting annoying......

2 items of note..the vanity sinks are vented by a Studer vent which terminates up in the attic above them. Also, the system is on septic....and none of the other 3 bathrooms or the kitchen, have this issue....

Appreciate any help!

 

[Diehard]

Looking at your sketch, I'm not totally sure which way the flows are. But it looks like it's likely that you have not properly vented the traps.
Traps must have a vent within a certain distance of the trap weir, based on the diameter and slope of the trap arm(down stream side of trap). Too much slope and/or distance will allow a siphoning of the trap(s).
Here's the requirements per the Uniform Plumbing Code, which would probably apply to you.


EDIT: I should note that those maximum lengths shown in the chart include a little factor of safety assuming the slope is right on.

 

[CT18]

Is the washer dumping into the 1 1/2" plumbing on that studor vent

 

[Borrego]

Looking at your sketch, I'm not totally sure which way the flows are.

flows from the laundry to the toilet.....vent locations should be close to correct. There is a 2 ft drop where the pipe drops from the wall to under the tub......?

 

[Borrego]

Is the washer dumping into the 1 1/2" plumbing on that studor vent

Yes.....but the odor does not occur when we're running the washer. I do hear a lot of gurgling noise when the washer is draining.....

 

[Borrego]

It seems like the traps are getting siphoned...? but how could that happen while the water is running?

 

[CT18]

The drain is to small for the washer to dump into. Also air needs to move both ways when a pumped line discharges like that, the AAV only lets air in. When you introduce a large volume of water like a washer into a line that is full of air, it needs to go somewhere.

 

[Diehard]

@CT18's quote, "When you introduce a large volume of water like a washer into a line that is full of air, it needs to go somewhere."
That may be one of the reasons AAV's are not approved for use in California.(If that's still the case.???)

So if it's flowing from the shower towards the toilet that would make the vent for the shower trap how far down stream? And does that 2" vent line come off the drain line above the centerline?

Would be nice to see an elevation view of the traps, slopes of piping and distances to vents.

Is that washing machine one of those new High Flow washers? If so, it''s waaay undersized. (But that's not your only problem.)

The traps get siphoned when the water stops running through them, due to in adequate venting and/or when a high flow passing through the common drain line is inadequately vented. Without a clear picture of how it's all connected together, it's all guess work.

EDIT: When that washing machine discharges, it's likely siphoning the sink trap since there is no functioning vent for that drain line. While the machine is discharging, there's a column of air compressing up on that AAV, not allowing it to open.
The shower may be a different case, as I already alluded to, above.