I am adding a second vanity to a bathroom. It will back up to the plumbing wall for the bathtub. No other plumbing on this side of the bathroom. Is there a way to drain the new vanity into the tub's drain system? Thanks.

More details please! How will you vent your new vanity? You will connect vanity to the toilet may and connect the bathtub to the vanity drain where it will be wet vented by the vanity vent. The image shown below is a typical installation. More questions? I'm as close as a click. Good luck, Tom

Hi Duski

If wet venting is allowed in your area then all you should need to do is to connect into the tub VENT at about 16-17" to the center of a sanitary tee fitting (off the finish floor) and run a pipe into the new vanity (install ptrap) and you should be all set in terms of drain/vent for the new sink.. ;)

Mark

I do not seem to have a vent pipe on thos side of the bathroom to drain the new vanity into. The current vanity, toilet, and stack are on the other side.
Can I hook it into the tubs horizontal drain pipe after the tub's trap somehow? I guess it cannot go to the tubs vertical overflow tube? I can send pictures but I can't figure out how to attach them here. Thanks.

There should be a vent, but if it is not there then you can connect into the tub horizontal drain line for the new vanity, BUT you'll need to add a vent to the sink drain... if allowed in your area, a mechanical vent (called an AAV) can be installed under the new vanity sink... ;)

Mark

I will look further for a vent pipe after I get in there but it is good to know about the AAV option. Is the only potential downside that the AAV might fail and you get a sewer smell until you replace the valve? Thanks for your help.

The only downside is that the AAV can fail (as you said)... why you place it in a "readily accessible" location like under your vanity.