Hello, my home I purchased recently used to have a washer and dryer put in for downstairs tenants in a storage room. At the time I capped off the pex supply lines and drain and never thought twice about it as I wasn't going to use this. In this room is also what appears to be the main drain from the upstairs kitchen island, and a plumbing cleanout. I framed a knee wall with an access panel for the cleanout to hide all this and turned it into a bedroom.
Then I had a ridiculous idea of doing a cool rustic minibar in this room as it fits the theme I have going. Knowing there was a washer there previously I figure this should be easy, that being said, I don't trust the previous owners of this house to have ever done anything correctly, as I have yet to find anything done correctly.
The concern I have is whether this drain is actually vented properly, not that I know much about venting. My guess is that the current plumbing looks as so; kitchen island sink, trap, vented to roof from first floor, drain goes down to basement, previous washer drain tapped into that drain with 3ft of pipe to a trap below my capped off section. From what I understand this is NOT an okay method of venting this, it is possible it's vented elsewhere and fine, it would have been in use before as their tenants did use this setup. If I go through all this pain of destroying my beautiful new drywall to tap into these lines and find it's not draining well or water being sucked from the trap, would installing an AAV alleviate these concerns?
Thank you.
Then I had a ridiculous idea of doing a cool rustic minibar in this room as it fits the theme I have going. Knowing there was a washer there previously I figure this should be easy, that being said, I don't trust the previous owners of this house to have ever done anything correctly, as I have yet to find anything done correctly.
The concern I have is whether this drain is actually vented properly, not that I know much about venting. My guess is that the current plumbing looks as so; kitchen island sink, trap, vented to roof from first floor, drain goes down to basement, previous washer drain tapped into that drain with 3ft of pipe to a trap below my capped off section. From what I understand this is NOT an okay method of venting this, it is possible it's vented elsewhere and fine, it would have been in use before as their tenants did use this setup. If I go through all this pain of destroying my beautiful new drywall to tap into these lines and find it's not draining well or water being sucked from the trap, would installing an AAV alleviate these concerns?
Thank you.
, I've actually decided to forego the sink but am still curious. 
