View Full Version : Question about vent layout

10-06-2009, 08:30 PM
I'm looking at moving the plumbing for my laundry to a new location on the main floor. The problem is, it's an exterior wall with no nearby vent stack. There is currently a utility sink nearby, but it's vented with an AAV (air admittance valve) but I'm not sure if code allows them in the area.

I'm looking for advice on options for venting the washer drain. There is a toilet and a floor drain about 12' away from where I'd like to put the washer drain, both have a vent accessible from the basement. I see a couple of options, but I'm not real confident that either is up to code.

1. Use an AAV on the washer drain. Does code allow this? Is it a bad idea to vent a washing machine this way?

2. Vent the washer drain to the toilet/floor drain vent in the basement. This would require dropping the vent stack down and then horizontally about 12'. I assume I'd at least need to bring the vent up to 6" above the washer drain before doing a 180 back down. Is going down with a vent stack a bad idea?

I hope this makes sense and someone can give me some good suggestions.

Thanks in advance

10-06-2009, 11:19 PM
You can't run the vent back down. You have to keep it going up up up.

10-07-2009, 03:13 AM
An aav is a bad idea on a washer drain because the aav lets air in not out. Washers are a pressure drained fixture.

10-07-2009, 05:43 AM
Thanks, that's what I thought but I had to ask.

So do I have any options other than cutting into the wall and putting a new vent in? I really don't want to tear apart all my walls to get a vent in.

What is the requirement for the vent elevation? If I drop the drain low enough and put the trap in the basement, can I vent it horizontally to the floor drain vent? In other words, does it just have to be 6" above the trap or is it 6" above the top of the stand pipe? I'm not really constrained in the basement since it's a crawl space and along the outside wall where it would be out of the way.

10-07-2009, 05:45 AM
6" above the flood rim....before you an angle away to where ever your going...like the others said don't use an AAV here...

10-07-2009, 05:59 AM
Dropping the vent down, as long as it does not create a pocket, will work, even though few, if any, inspectors would allow or approve it. You are venturing into the gray area between what is proper and what works.