Trap arm height relative to hanging cabinet

[Bschooly]

I'm remodelling a bathroom where a traditional vanity is being replaced with hanging variety. Trap arm exits wall at about 13 inches. Too low for cabinet.

Is my only choice to move the trap arm up the stack? Can I plug the old location or does it need to come out? See picture.

 

[Reach4]

You could plug that in place, I think.

Is it close? Probably not, but if it were, you could do something like this from https://terrylove.com/forums/index.php?threads/help-with-dwv-under-vanity-with-drawer-the-trap-will-siphon.84565/:

 

[Sponsor]

 

[Bschooly]

So the AAV negates the height requirement of the trap relative to the sanitary tee?

Doing this would mean about 4" of pipe exposed under the cabinet (as the bottom of the cabinet is 15" from the floor). Might be OK; not noticed...

 

[Reach4]

So the AAC negates the height requirement of the trap relative to the sanitary tee?

Under that AAV, there is a new sanitary tee that the trap connects to.

I would use a slip trap with a trap adapter, rather than the glued trap.

As an alternative, you could have the elbow and new trap adapter in the wall rather than outside of the wall. The AAV needs to be accessible for service. It could be behind a vented plate, or maybe you could even bring the pipe from the top of the new trap adapter back through the wall at 45 degrees. Then turn the pipe back vertical with another 45, and have the AAV under the sink. I don't know if there is room for all of that.

 

[Bschooly]

I'm obviously not an expert but can I add a dry vent and try that back into the vent stack? See image.

 

[Reach4]

I'm obviously not an expert but can I add a dry vent and try that back into the vent stack?

Even better.

Run horizontal for the vent 42 inches above the floor (6 inches above the flood level of the sink) or higher.

 

[Bschooly]

What diameter? Wonder if there is a technique for tying into cast iron in situ...

 

[Reach4]

What diameter? Wonder if there is a technique for tying into cast iron in situ...

I think 1.5 or larger.

If trying to insert something into cast iron, strongly support what will stay, before cutting. Riser clamps can help with that. Then use two shielded/banded couplers to insert a PVC pipe section with the fitting(s) that you need. The AAV avoids that.

To select the couplers, measure the OD of that cast iron that you propose to cut.

Or maybe tie the vent pipe into the attic to something smaller.

 

[Bschooly]

OK. Thanks. I also saw https://www.fernco.com/sites/default/files/literature/fernco_tapsaddle_install_0.pdf

Don't know which is easier and best...

 

[Reach4]

OK. Thanks. I also saw https://www.fernco.com/sites/default/files/literature/fernco_tapsaddle_install_0.pdf

Don't know which is easier and best...

Saddle would probably be easiest, and the shielded/banded couplers would be allowed by code.

 

[Bschooly]

Thanks Reach4 for all your answers.