New bathroom vanity and rerouting drain

[DIYShaun]

So I'm new to this forum as I wanted to get a professional...or at least someone that knows what they're doing....advice. I purchased a bathroom vanity and will also be installing new tiling. Now due to the updates, the new vanity I have does not clear the existing ptrap and I do not want to cut into the new vanity as it just looks half assed.

My plan is to move the drain line up about 6 inches, roughly in line with the supply line valves, in order to have proper clearance for the ptrap. Now where the existing drain line was I will have to cut into the existing pipe and basically put 2 elbow after the Ptrap to connect to the existing drainage line in the wall. I just wanted to know if 1. is this legal and 2. will this cause any draining issues?

What I picture it looking like is water going through the P-trap for about a foot or so, down a 90 vertically then down another 90 to make the vertical to horizontal transition which then leads the water to the existing drain pipe.

I know exactly how I'm routing this, just need to know if this is legal. Thanks for taking the time to read!

 

[Terry]

No, not legal, or a good idea.
The venting comes off the top of the arm to the trap to prevent the trap from siphoning dry. When you no longer have a water seal, the sewer gas invades your home and stinks up your bathroom. A nice smelly odor while brushing your teeth.

Here an Auto Air Vent was added for venting.

This was another way.

 

[Sponsor]

 

[WorthFlorida]

I'm assuming you are installing a wall hung vanity or at least one with an open bottom. There are other kinds of traps that can be used and may fit the look you are going for. Google "bottle traps".

 

[DIYShaun]

Okay, so let me clarify on this one. First, Terry thanks for the much quicker than anticipated response! So the pictures you posted are literally how I intended to replumb the drain line (exluding the attached vent). I do plan on obviously keeping a ptrap under the sink, but just to raise where the existing drain line is to use 2 90s. I also just learned how to draw on a picture in my gallery, so I'll attach that to how I plan on running the new drainage. Keep in mine the purpose would be to get the drain line coming out of the wall in line with the supply lines. Where I have the "X" are where I intend on putting the 90s. One to raise the height of the drain transitioning from horizontal to vertical then the other to have the 90 extend outside of the wall that leads to ptrap.

 

[Terry]

Without the added AAV the trap will siphon.
If you were to pull a permit and adding the two 90's the way you indicate, it would fail.
Once you raise the arm, it needs the added venting.

What you have now.

 

[DIYShaun]

Okay, thanks for clarity. That was my concern was the siphoning. So when you look at drain lines, does it need to be a straight line from the appliance to the main drain line? Obviously with the naturally 1/8 in slope per foot.

So I could do what I was originally referring to, I would just need to add the vent on top of it? If I felt like getting frisky, could I just cut the dry wall back to the main drainage line and just redo the plumbing through the studs similar to what you provided in the 2nd picture in the rough in construction. Basically cut out the existing pvc adapter, move it up a few inches, then run the new pipe through the wall?

 

[Terry]

Cutting the wall and moving the santee up would do it. Fer sure.

 

[Reach4]

Obviously with the naturally 1/8 in slope per foot.

1/4 inch per foot is the number.