Dual Vanity Plumbing Review

Users who are viewing this thread

DIY_Novice

New Member
Messages
12
Reaction score
0
Points
1
Location
IL
Hi all,

I've looked at quite a bit of dual vanity setups on the net but I'd rather not cut into the iron pipe here if I can help it. I also bought a dang vanity that has several drawers directly in the center between the two sinks. I've attached a blank photo and a proposed photo. Does anyone see any issues? The area that is X'd out is the vanity drawers so I'd like to avoid that area if possible. Do I need the blue line for vent? Main stack is slightly visible on bottom left.

Maybe a little hard to visualize but the red lines coming out of the wall area coming "out" of the screen, where the P-trap arm would attach.

Single vanity as-is:
20210807_131954.jpg


Proposed setup:
20210807_131954_plumbing.jpg


Alternatively I could try this, but I'm not sure if I will be able to make the 90 right there, the top "port" is a little more offset to the right than the lower.
20210807_131954_setup2.jpg
 

Terry

The Plumbing Wizard
Staff member
Messages
29,942
Reaction score
3,459
Points
113
Location
Bothell, Washington
Website
terrylove.com
There are some fittings that need changing.
A vertical dropping into a horizontal is a wye, combo or long turn 90.

A trap arm going to a vertical is a santee.
Each trap arm needs a vent above the arm, not below.

double_lav_right_side_5.jpg
 

wwhitney

In the Trades
Messages
6,556
Reaction score
1,841
Points
113
Location
Berkeley, CA
Does the "tee" fitting at the bottom right of your existing photo have any curvature to it at all, or does descending water just hit the middle of the bottom of the tee, with nothing to direct it l left or right? If the latter, that makes replacing the tee required.

If you don't want to deal with the connections between the iron pipe and the stack, you can carefully cut each horizontal pipe in the stud bay next to the stack, and use a fully shielded rubber coupling to transition to plastic. You'd be better off removing all the iron pipe and adapting from plastic to cast iron at the stack. And if you cut into the bottom horizontal and find alot of rust buildup on the interior of the iron pipe, taking it back to the stack is a necessity.

As to your drawings, you'll have more options if you are replacing iron pipe. But the first one is OK, and for IL under the IPC, in the first one the blue vent is not required. You just need one vent connection on the horizontal red line in the wall, anywhere along there, as long as the distance from the vent connection to the right hand trap is under 6' and the total fall is no more than one pipe diameter (1-1/2"). Putting the vent connection in the middle between the two stub outs would be conventional horizontal wet venting. And again if the existing tee on the vertical iron pipe is not a sanitary tee with some curvature, it needs to be replaced.

The second picture is not allowed; your right hand trap needs to be vented before the drain falls more than 1-1/2". So that vertical segment in the wall on the right is prohibited.

Cheers, Wayne
 

DIY_Novice

New Member
Messages
12
Reaction score
0
Points
1
Location
IL
Terry, wwhitney,
Thank you for your replies.

I'm not totally opposed to tapping into that cast iron, I just don't want to mess with the oakum/lead OR main stack very bad. It looks like I could get into the main stack at these threaded fittings pretty easy though? This is just to the left compared to my original picture. Is there anything I need to be careful of here at the cast to PVC transition? It's just a Schedule 40 PVC MPT adapter with some pipe dope, right? No bonding agent required?

How careful do I need to be trying to get the old cast iron un-threaded? I'm guessing it's not going to want to unthread willingly :)

20210807_172525.jpg


20210807_172535.jpg


If getting into the main stack like above is easy enough, then it looks a lot more straight forward to me -

20210807_131954_setup3.jpg
 

Terry

The Plumbing Wizard
Staff member
Messages
29,942
Reaction score
3,459
Points
113
Location
Bothell, Washington
Website
terrylove.com
If the pipe doesn't thread out, you can cut and use a shielded coupling. Replacing pipe on the vents don't matter so much, it's more for the waste that it helps.
 

DIY_Novice

New Member
Messages
12
Reaction score
0
Points
1
Location
IL
Can anyone help identify what size pipe this is? I measure the pipe at 1 7/8" OD and 1 3/4" ID. I've cut the metal horizontal pipe to the right of the circles in red and wanted to use a hub coupler but the 2" shielded hub coupling I bought (https://www.lowes.com/pd/Fernco-2-i...ded-Specialty-Coupling-PVC-Fitting/1000075337) is incredibly loose on the iron pipe (fits the 2" PVC perfect). Did I somehow buy the wrong coupling? It looks like iron pipe to me (galvanized?) and not cast iron, but it doesn't match any table for iron pipe I'm looking up.

20210807_172525.jpg
 
Last edited:
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