Kitchen sink question - bow vent

[Endymion]

Hi, new to the forums, hopefully I can keep this concise.

I'm repairing an existing island kitchen sink that was installed without proper venting. Due to multiple obstructions in the cabinet (conduit, built in soap dispenser, copper supplies) and below (web joist, hvac trunk, more copper) I have a very small window in which to add the additional pipe for the other half of the bow vent. Currently there is a 2" PVC drain stubbed up into the cabinet which is then reduced to 1.5" and then connected to the sink drain. My question is this; it would make my life much easier to work only with 1.5" inside the cabinet space and have the drain line tie immediately into the existing 2" drain line in the floor, but could that cause problems down the road if the house is for sale and an inspector looks under the sink and sees only 1.5" PVC?

I have access to the ceiling below, the only real challenge is finding space to install the bow vent. Thanks in advance for any advice!

Edit: Kitchen sink, dishwasher, and garbage disposal all go thru that drain.

 

[DIYorBust]

Just apply to the town for a variance.

In seriousness, I think you understand the risks. It'll probably work.

 

[Sponsor]

 

[OLD TIMER]

Can you install a STUDOR VENT ?

 

[hj]

I usually use 1 1/2" pipe above the sink connection over to the top of the REQUIRED cleanout in the vent.

 

[Endymion]

I usually use 1 1/2" pipe above the sink connection over to the top of the REQUIRED cleanout in the vent.

That's what I'm going to do. I was able to find space to keep the 2" on the drain side, but still reduce it to 1.5" above the sink connection and then finish out the bow. I'm installing cleanouts on both the drain and vent side.