Sewage odor eminating from 1st floor bathroom/laundry room

firsthomenewb · 11-30-2007, 12:11 PM

Hi and thanks for reading!

I own a two-story house in southern Michigan, with full basement, 2 1/2 bathrooms and a laundry room. House is three years old (finished Oct 2004).

In the past year, we have been getting raw sewage odor eminating from the 1st floor bathroom sink and utility sink in the laundry room. All plumbing in the house converges into a 3 1/2" outlet pipe to the local sewage lines in the basement.

I checked the traps, they've got water. What I can't find though, is a vent pipe! Having done some reading here on the forum, I conclude that a vent pipe should be running off the main drain line, through the house and out the roof, correct? Also, the trap in the bathroom has a local vent just before the down bend (charcoal filter). I'm considering removing that vent and capping it off.

Running water through the sinks usually (not always) gets rid of the odor, but that's expensive and wasteful.

What should I be looking for, and how to fix?

Marlin · 11-30-2007, 04:06 PM

You could try using some sort of cleaner, maybe you just have buildup in the trap that stinks. They probably make something specifically for this.

The other scenario is a clogged vent causing the traps to dry out.

skymaster · 11-30-2007, 05:21 PM

First:

Are you saying that there is NO VENT in your system? There has to be a main vent stack to which all your branches tie into. As far as this bathroom vent??????/ Please explain this with more detail. There should be NO OPEN VENTS ANYWHERE a system

firsthomenewb · 11-30-2007, 07:48 PM

Here are pictures of my plumbing drains:

This is off the kitchen and laundry rooms:

..and here is the drain for the bathroom sink in question, with toilet:

What do you think?

firsthomenewb · 11-30-2007, 07:51 PM

..and here's the trap and vent for the offending sink:

Marlin · 11-30-2007, 08:05 PM

I can't tell much from your pictures. It looks like under the sink you have an AAV on a backwards horizontally installed sanitary tee. That whole setup is completely illegal.
*A sanitary tee can not be used on it's side
*If you were going to do it anyway you would face it the other direction so air would flow up it
*That vent needs to be above the flood plain of the sink

If the smell is coming from the sink the AAV is probably malfunctioning either staying open allowing sewer gases in or sticking shut causing the trap to get sucked dry and sewer gases to come up through the sink drain.

firsthomenewb · 11-30-2007, 08:09 PM

okay, you win..what's an AAV? and what makes it illegal/nonconforming?

firsthomenewb · 11-30-2007, 08:12 PM

found it..Air Admittance Valve. doing some reading now...

Marlin · 11-30-2007, 08:13 PM

AAV stands for air admittance valve. It is used in place of a vent. The valve itself is fine, the way they installed it is wrong. Check my above post for the reasons.
Personally I would just change the valve and not go tearing walls out to re-pipe it correctly so long as it works. You probably feel the same way.

firsthomenewb · 11-30-2007, 08:21 PM

...so I should replace the T as well? I see what you're saying about it,BTW..the design of the T demands that it be vertically installed. It also slopes upwards as it enters the back of the cabinet and wall.. That can't be good.
What's the proper way to fix this?

Oh, and as soon as I removed the valve, I could feel air being sucked into the pipe! And then, the sewer smell hit me. So I put the valve back on.