My kitchen sink and washer (in the basement) sewer drains connect in a closed system to a sewer pipe 50 feet away from the main stack (I think it is a second sewer line because it doesn't seem to enter the main stack). It is not vented and the kitchen sink bubbles and gurgles when the washer empties. In addition, when the sink drains I have concerns that it might empty into the washer if a large amount of water goes down the drain. I want to install a dishwasher (not present now) as well as a garbage disposal. I do not want to do this before I add a vent to this line. Do I have to run the vent up through the three floors of the house to the roof or can it be vented through the exterior wall?

Hello Jminarcik,

You could install vent through the wall to the exterior and then run it surface-mounted all the way above the roof. Exposed section of vent should be Cast Iron. If plastic (ABS or PVC) than it would have to be boxed in.

In my area of operation, you cannot terminate vent horizontally on exterior wall.

Better option is to install so called AAV vent ( Air Admittance Vent ) under the kitchen sink. This vent is legal in some states and not legal in others. Call your Inspector and ask him. AAV installs right after kitchen trap and admits air during sink draining eliminating gurgling sounds. See the pic...

I suggest that you install AAV vent on existing washing machine drain as well...

Hope that will answer your question. Good luck with your project. Milo

Thanks Milo. According to current code they are legal to install. Is there any concern installing one after a garbage disposal?

As for installing one on the washer drain, my thought would be it might leak/foul if the kitchen sink were to back up since the vent would be lower then the water line of the kitchen sink. Is this a concern?

Thanks again!

That should not be a concern. Here is why: Dishwasher drains to Garbage Disposer and Garbage Disposer drains into Branch T before P-trap. AAV is then installed after P-trap.

AAV vent, installed lower then Kitchen Sink should not leak since it is One-Way device. It is like a snorkel: it allows air IN but seals against Odor and / or water backing out.