Rough In Vent Stack

[Kamabuki]

Greetings All
I've been reading all the great information and help everyone is providing on this Forum so I thought I would join up. I am currently stubbing in plumbing for a downstairs bathroom sink with a kitchen sink above on the second level. My question is regarding the Vent stack. Reference attached drawing - is this an acceptable stack up?

 

[Terry]

That should be fine as long as there is a full vent somewhere else in the system.

 

[Sponsor]

 

[Shacko]

Don't forget that AAV'S should not be concealed

 

[Pigrew]

I'm a newbie at this, but I'd wonder what the horizontal distance is between the sinks and the soil stack. My understanding is that there is a maximum horizontal distance between the p-trap and the soil stack (which depends on the local code). Also, (please correct me if wrong), but there is no need for the AAV to be many feet above the sink. The AAV that I just purchased says that it only needs to be 4 inches above the trap.

Furthermore, I don't think that you would need both an AAV and a vent for the upstairs. You need a vent (somewhere), but if that fixture is vented, you don't need an AAV.

It'd be great if someone could confirm or reject my above statements... I need to figure out these issues for my house too.

 

[Terry]

Each fixture must be vented within 42" of the trap horizontally.

The upstairs will need a vent
and the downstairs will need a vent.

The vent needs to be between the p-trap and the main waste stack.

A standard vent is much preferred. Mechanical vents will fail and need replacement at some point. They also must be accessible and can not be buried. If they are in a wall, then you need a vented cover that allows air to the valve.

 

[Kamabuki]

Yep I read the minimum 4" above the trap but I figured if 4" is ok then 48" must be better. The lower level AAV is stubbed into a wall which I have put into a vent box with a louvered panel. The upper AAV is vented into the attic approx 12" above the insulation. I could have vented the main vent stack through the roof but I did not want the hassle and added expense of adding the roof vent flashing.

 

[hj]

4' or 48", it does not make any difference. The real problem is that an AAV cannot relieve a positive pressure, and that is what the water draining from the upper sink will create at the lower one.

 

[Pipehacker]

Each fixture must be vented within 42" of the trap horizontally.

The upstairs will need a vent
and the downstairs will need a vent.

The vent needs to be between the p-trap and the main waste stack.

A standard vent is much preferred. Mechanical vents will fail and need replacement at some point. They also must be accessible and can not be buried. If they are in a wall, then you need a vented cover that allows air to the valve.

Terry, your new Carhart jacket with embroidered logo looks very professional.

 

[Kamabuki]

4' or 48", it does not make any difference. The real problem is that an AAV cannot relieve a positive pressure, and that is what the water draining from the upper sink will create at the lower one.

I see what you mean by the positive pressure that the upper sink will create at the lower one. If I'm looking at this correctly the ideal way to drain the upper sink would to have it's drain attach to the vent stack below the lower sink drain point at the main vent stack. Unfortunately that is not possible as the main vent stack comes out of a concrete slab 6" thick and the lower sink's drain attaches just inches above where the main vent emerges from the concrete allowing no room for another drain attachment below the lower sink attachment. If you could - take a look at the re-designed vent stack up drawing attached and give me your thoughts. Is this a better way to vent/drain both sinks? Also note that I have removed the AAV from the main vent and will vent it through the roof.
Thanks for all the input. Much appreciated.