Can I Improve The Drain Location On This Double Sink Vanity?

[Sean493]

Hi Everyone,

I wanted some guidance on Improving the look and functionality of my double sink vanity as I'm replacing it with a new one that has drawers in the center and would like to not have to block / cancel them out since the original setup of the drain is running right through them. Currently, the drain for this double sink is set up like a double kitchen sink, one P-Trap for two sink basins. The main drain appears to have a Sanitary Tee coming in from the left side of the vanity, not the backside like most vanities. So it's running perpendicular to vanity (pictures attached below)

I would like improve this drain design, while complying to all NJ Plumbing Codes.

To my understanding according to most plumbing codes the trap arm (the distance from the sanity tee to the P-Trap) can only have 135 degrees of change for 1-1/2 DWV trap arms?

Since, behind the 66 inch vanity's sheetrock there is plenty of space and I mocked up a potential solution to my problem. Please let me know if it would work and is complaint to NJ plumbing codes.

Also can you use an a AAV in 1-1/2 setups?

Thank you.

Old Drain Setup:

Diagram of Old Drain setup:

Diagram of proposed New Drain setup :

 

[wwhitney]

Comments:

- NJ allows AAVs under Appendix E.8 of the NSPC
- NJ allows a 1-1/2" wet vent
- NJ allows up to 3 DFU on a 1-1/2" horizontal branch
- AAVs must be accessible, so if the combo takeoff is within the wall, you'll need a ventilated wall box to contain the AAV, and you'll need to ensure it is accessible for future replacement of the AAV.
- The combo takeoff for the AAV is backwards; if water ever gets into the riser, it should be direct to drain towards the stack.
- Your previous configuration was not allowed by the NSPC unless that horizontal segment between the lavs was 30" or less.
- NSPC 5.4.13 Exception 1 says a 1-1/4" tubular trap (which is removable) may be used as the cleanout for the a 1-1/2" drain.

Cheers, Wayne

 

[Sponsor]

 

[Sean493]

Comments:

- NJ allows AAVs under Appendix E.8 of the NSPC
- NJ allows a 1-1/2" wet vent
- NJ allows up to 3 DFU on a 1-1/2" horizontal branch
- AAVs must be accessible, so if the combo takeoff is within the wall, you'll need a ventilated wall box to contain the AAV, and you'll need to ensure it is accessible for future replacement of the AAV.
- The combo takeoff for the AAV is backwards; if water ever gets into the riser, it should be direct to drain towards the stack.
- Your previous configuration was not allowed by the NSPC unless that horizontal segment between the lavs was 30" or less.
- NSPC 5.4.13 Exception 1 says a 1-1/4" tubular trap (which is removable) may be used as the cleanout for the a 1-1/2" drain.

Cheers, Wayne

Hi Wayne.

Thanks for your reply and advice!

After some further investigating and cutting open some more sheetrock, some of my assumptions were wrong. I made updates to the drain diagrams and had a few more questions that would help me better understand how to fix this drain setup, if you don't mind.

The first important thing I realized was that the new drain will have to enter the side of my new 66 inch vanity at a 45 degree offset, due to a structural concrete pillar blocking my ability to run the new drain completely behind the sheetrock.


I updated the old drain diagram to give you a visual of how the actually drain is routed:

Here is the updated proposed new drain diagram showing where the concrete pillar is :

Wayne, please let me know if this updated diagram looks alright to you / is up to code? I took your advice and fixed the direction of the second combo wye.

1) Additionally, since the trap arm exceeds 135 degrees in turns from the main stack, will the vent to the first sink drain be cut off and no longer functioning? Is that okay?

2) If statement 1 is correct, does that mean both sinks will be venting through the one AAV?

3) Additionally, based on what I've described regarding this double sink setup, do you know of a better or more logical way of designing this new drain setup? As you mentioned, the current/old setup is not code compliant because the horizontal run between the two sink drains is more than 30" inches apart (it's about 33 inches apart).

Looking forward to your reply.

Sean

 

[wwhitney]

0) Looks fine. You could omit the topmost (in the rendering) 90 degree bend (which should be a LT90) and just let the branch drain continue at a 45 until it reaches the back of the cabinet and can hit a 45. But perhaps that takes up more room in the cabinet than you like.

1+2) I don't know what you mean by "cut off". In the diagram shown, both sinks are relying on the AAV for venting, which is fine. The right hand sink is dry vented, while the left hand sink is wet vented by the right hand sink. This would be true even if your stack were located where your concrete column is and you had no bends between the horizontal combo where the two sinks join and the stack.

3) Nothing comes to mind as far as connecting to the stack in the current location. If you were opening up the floor, say, you would have other options which might or might not be preferable, but certainly aren't worth opening up the floor just to do.

Cheers, Wayne