Yet another single-to-double vanity conversion...please help!

Users who are viewing this thread

MartinP76

New Member
Messages
3
Reaction score
0
Points
1
Location
Ontario
Hi All,

I know that this is a well-covered topic, and all of that information is much appreciated. Based on previous posts, I think I have a possible solution to my problem, but would appreciate any advice you might have. I also wanted to say, that it is amazing that so many professionals are willing to help out DIYers like me.

I have attached photos below, but here is a summary of the situation. I am installing a 54" vanity in a 54 1/2" space (tight, I know). The vanity has two open cabinets (15"w x 18 3/4"h inside dimensions), with a set of drawers in the center (3 1/2" gap between back of drawers and wall).

The current drain pipe is slightly off-center on the wall, with 29 1/2" (from center) to the left wall, and 25" to the right wall. Based on other posts, it looks like I have 3 options:
1) Cut out the existing T connector (which will be fun, given the proximity to the double 2x4"s), and replace it with a wye.
Issue: The second vent pipe is 2" away from the one I'm working with (right), so I would have to immediately come out of the wye with a 90-degree and bring the plumbing outside of the wall to get past it. There is space, though I'd have to notch the back of the vanity, but this won't be seen, really.

2) Leave the current T connector in place to serve the right sink, then cut above it and add a second T (so 2 Ts, stacked vertically) to serve the left sink.
Issue: Besides the fact that there is already a 90 glued in, and I need to extend this further, the issue is that the second T connector is going to be about 4" higher, and the vanity cabinet is not that tall. Currently, the drain is 16 1/4" off of the ground; I will need to install the vanity 11-12" off of the ground (it's one of the floating ones), giving me about 5" clearance below the current drain, and about 13" above. Adding that second T 4" up reduces this to 9" for the P-trap. Doable, but tight I wonder?

3) Same as option #2 for the right sink, but then I cut a T into the left-most vent pipe for the left sink. In other words, the two sinks drain down different pipes.
Issue: This stack is either venting the kitchen below the bathroom or is serving the rough-in for a powder room in the basement. In either case, I don't really know the consequences of tying into this vent stack.

I would love to hear what the experts would recommend - one of these options, or something else? I've done lots of DIY plumbing in the past, but I've also called in a plumber when the work exceeded my skills, so if you honestly feel like this is one of those cases, let me know. Thanks in advance for your advice.

p76-02.jpg


Please ignore the 30 1/2" marking at the bottom - that should read 20 1/2"

p73-03.jpg
 
Last edited by a moderator:

Terry

The Plumbing Wizard
Staff member
Messages
29,942
Reaction score
3,459
Points
113
Location
Bothell, Washington
Website
terrylove.com
DO NOT DRAIN A LAV DOWN A VENT PIPE.

Don't do that.
Take some drywall off and move the vent farther to the left.
Since you have 2" coming up, cut a 2x1.5" santee down lower for one lav, and stack a second tee on top of that for the second lav.
The top santee can be a 2 x 1.5 x 15
The lower tee is a 2 x 1.5
Wet venting is done with 2" pipe, so keep that in mind. The trap arm is 1.5".
 
Messages
705
Reaction score
48
Points
28
Location
Montreal, Canada
First all, good pics, and good diagram. Best way to get fast help here.

Why do you need to open the wall at all?

Everything in the photo was already working there for a single sink, right? Why not just treat this like any kitchen double sink and share one trap?

You did say you have space in the vanity, so you can do whatever fancy there instead, without touching anything inside the wall.
 

MartinP76

New Member
Messages
3
Reaction score
0
Points
1
Location
Ontario
Thanks so much for the quick replies!

standardairconditioner: Unfortunately, the layout of the vanity (drawers in the middle) don't allow for a double-kitchen sink solution, but I appreciate the advice, and attempt to minimize the changes - believe me, if I could, I would.

Terry: Admittedly, a few of your points confused me (see below), but based on your suggestions I think I understand what you're suggesting. If you don't mind, I drew up some (close to) scale diagrams of what I think you're saying below (top down, and front views). Basically, start from scratch (cut out existing) and replace with two stacked santees, one for each sink. I'll need to play with heights/slopes to make sure it drains properly, and for the left-hand sink I'll need to sneak past the existing downstairs vent and notch the vanity cabinet, but it should work. The one issue is I think I can only get the 2" x 2" x 1 1/2" santees in 90 degree Ts, versus those with the 45 degree gradual - will that be an issue? I know you suggested ones that are 2" x 1 1/2" x 1 1/2", but since the vent and drain are both 2" (i.e., up and down), unless I cobble together some sort of reducer for the top or bottom to get me back up to 2", it won't work with the existing setup. Should it work/pass code as I've drawn below?

I'm also confused by your last statement about wet venting - when I had the plumbers do the rough-in two years ago, there was no mention of wet venting, but wouldn't that be the case if I tied in to the left-most, downstairs vent, which you told me to do (i.e., using a vent pipe as a drain as well)? Probably just a dumb DIYer, but I was confused by this.

Thanks again, in advance, for your help with this.

p76-04.jpg


p76-05.jpg
 
Last edited by a moderator:

MartinP76

New Member
Messages
3
Reaction score
0
Points
1
Location
Ontario
Hi Terry,

Again - valuable information, thank you. Are you actually saying that a trap arm can have too much rise? I didn't know that - I always assumed it was a minimum. Good to know.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks