Combine a vent stack?

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1111ron

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I have two vent stacks (2") that are the farthest upstream from the sewer and I'd like to combine them if possible. Having a new roof done and trying to eliminate as many breaches as possible. The vents are 6' apart. They were added by someone at a later date to the home for a washer in one room and the second for a water softener in the garage. Nothing else is attached to either. If possible I have two options;

1. Connect the two in the attic space BUT it will be difficult. The roof is low pitched, space is limited and due to the location it will require two tees and two 90s to combine them.
2. Install a AAV on the water softener vent in the garage. Easy access, easy fix but I'm always reluctant to use AAVs. Being that is a singular vent and drain seems a reasonable solution.

Plumbing-vents.jpeg
 

John Gayewski

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You can use an aav or just needs to be accessible and preferably above the flood rim of the fixture.
 

Jadnashua

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Combining vents is possible as long as you ensure the combined size matches the fixture units connected and you maintain a downwards slope to any horizontal sections so condensation or rain/snow that might get in there can drain. S Texas probably doesn't have to deal with enlarging it for frigid temperatures like is required in more northern climates to prevent hoar frost from closing it off as it goes through the roof.

As long as there is at least one atmospheric vent in the system, if the local codes allow, you can use an AAV on a branch. Atmospheric vents are preferred, as they don't fail and need to be replaced like an AAV.
 

1111ron

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You can use an aav or just needs to be accessible and preferably above the flood rim of the fixture.
Combining vents is possible as long as you ensure the combined size matches the fixture units connected and you maintain a downwards slope to any horizontal sections so condensation or rain/snow that might get in there can drain. S Texas probably doesn't have to deal with enlarging it for frigid temperatures like is required in more northern climates to prevent hoar frost from closing it off as it goes through the roof.

As long as there is at least one atmospheric vent in the system, if the local codes allow, you can use an AAV on a branch. Atmospheric vents are preferred, as they don't fail and need to be replaced like an AAV.

Maintaining a slope between them will be a challenge with the lack of space in that area of the attic. Snow, frost and freezing is normally not an issue here BUT the last couples of years has changed that. Being that each vent serves only one fixture the DFU is good with 2" PVC. I do have two other atmospheric vents downstream. One 1.5" serving a kitchen sink and further down a 4" between two bathrooms. I guess technically I could put a AAC on each and eliminate both vents because data says a AAC can handle a single washer or a softener drain. Both could be accessible and above the flood rims. Don't think i will go that far though.
Texas code I believe does allow them on branches but local codes vary. Will have to check my local code first.
Thanks!
sorry, don't know why it put your name on the reply.
 
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