Good day! I have an island on the 1st floor with a sink. I am getting rid of the sink. The drain vent runs up a decorative pillar (not weight bearing that I am getting rid of) in the middle of the room and to the roof on the 2nd floor. I am not able to see the drain connections at the bottom since it is a concrete slab so I am not sure what else it is connected to. (1) Since the sink will be removed can I just cut the drain vent and cap it at either ends (since there will be no pillar to hide it? (2) Will water enter the drain vent through the roof and collect in the capped portion? Thank you.

What size is the pipe coming out of the floor and does it remain the same size all the way through the roof.
If it is a two inch pipe I don't think it would be a vent for anything other than the sink unless it could be a vent for a floor drain, and I don't really think it is.
As far as the rain water building up in the pipe from the roof, just to make sure that it didn't I would cap the very top with something, if it was nothing else that a rubber ball stuffed tightly into the pipe

Let me pick up the parts that Letme missed.
You can cut and cap the vent only if there isn't another revented back into it in the attic. Or if you have a second floor fixture using the same vent.
Not if you cap the top of the vent as well as the base. I don't think a rubber ball's going to be all that permanent.
You should have nothing else connected to a island sink installation. If you don't ever plan on reusing the old drain why not simply cut the pipes off level with the floor. Jam a bunch of rags in the openings to make a seal and fill the top inch or two with cement.
That way you could tile or Vinyl right over it. Good luck and thank you for rating my answer. Tom

The pipe size is 1 1/2" and it is same size all way to roof.

Tom,

The vent pipe is 1 1/2" all the way to the roof. There is no 2nd floor fixture connected to same vent. I am not cutting the pillar all the way to the floor... just to counter height and putting a granite counter on top.. . hence I was thinking of capping. Is the isolation island sink connection a code requirement? Also do you think it is prudent to put an Air admittance valves (AAVs) on the cut part just to be safe... Thanks for your input.

Raj

Additional info:

Tom,

The vent pipe is 1 1/2" all the way to the roof. There is no 2nd floor fixture connected to same vent. I am not cutting the pillar all the way to the floor... just to counter height and putting a granite counter on top.. . hence I was thinking of capping.

Also, I can see vent pipes on roof for all the outlets for 2nd floor. But 1st floor... we have kitchen sink, dishwasher, clothes washer. And a 1/2 bath... for these I do not overtly see vents... is it possible that all these are connected to that single vent at the island sink that I am dismantling?

Is the isolation of island sink connection that you mention, a code requirement? Also do you think it is prudent to put an Air admittance valves (AAVs) on the cut part just to be safe... in case all the other 1st floor outlets are connected to this single vent? Thanks for your input.

Raj

Cut it as you wish and need. Cap it off on the roof and on the other lower end with Jim Caps. End of discussion.

Hello, to find out if the vent is tied to something other than the kitchen sink, when you cut the vent going up the pillar have someone run water on the washer and bathroom,and listen into the vent going up to the second floor,if there is something else tied to that vent you will hear the sound of water draining, if you don't hear anything then its safe to cap the vent on the roof. If you do hear sound of water draining through the vent then glue a slip cap onto the vent above the first floor ceiling, depending on how the vents are tied together you may or may not get any rain water down the vent, but glue a cap on to be on the safe side. Goodluck on your project. ----zeke----

It's very doubtful that other fixtures vent of your island sink vent the way it's described. Cut and cap off the open ends. A AAV isn't necessary as this will be a dead line. Good luck, Tom