adding double vanity

Good Afternoon all:

I am remodeling a hall bath and changing from a single bowl vanity to a double bowl. So, I have to add plumbing for the second vanity. Since I am also moving lights, GFI plugs, etc. all of the drywall is off the wall. My question involves the vent. I have a vent on the existing drain line. Do I have to install a separate vent for the new plumbing? If so, should I just go through the top plate and then tap into the existing vent in the attic? What is the appropriate plumbing solution?

Thanks for your help

Jim

Only if the new lav is too far away from the existing vent. And that depends on the size of the drain and the size of the existing vent and it's location. Draw something up with distances and sizes and post it.

Thanks for the reply Wally,

Vent is directly over one of the new sinks/drain. I was fortunate that the plumbing for the old sink was in exactly the right location for one of the new sinks
Vent and drain are 1 1/2". Second sink is 34" o/c from the other sink and vent.

Sorry about the non-drawing. This was faster if it gives enough information. Otherwise I will post a drawing

Thanks again,
Jim

Ok then, distance and size are not an issue so you will be fine with the one vent on two sinks. If Terry reads this I think he has a picture of a double lav piped up that is real helpful.

Distance is only ONE factor. HOW you install the piping for the second sink will determine what has to be done as far as venting, or whether you can even do it correctly using the existing piping. (This is a more likely scenario, but we would have to see how the pipes are installed.) Usually having the drain where one sink will be creates problems rather than solving them. A description by a novice is NEVER as good as a picture.

Hi again,

Ok, here are some pictures. I hope they help. The plumbing you see is situated so that I can use it for the right hand sink. The other sink will be situated 34" O/C to the left of the existing drain. I was going to separately plumb the supply lines and the drain, but I wondered if i couldn't just tap off of the supply lines and run across through the wall. This would be much simpler. The drain, however, I was going to take down through the wall just like the existing and splice into the main house soil line. The second picture shows where the existing drain comes into the soil line under the house.

Now that I think about it, it would be easier to come down through the floor...across to the existing drain...and tap into the existing drain below the floor and before the drain meets the house soil line. Is this advisable?

This is where my vent question came in. Is the existing vent ok to serve both sinks?

Thanks again for all your help

Jim

In this case, since the pipe is only 1.5" and the second lav is over to the left,
I would cut in a wye below the first lav, run over to the second lav,
The pipe turns up with a long turn 90
For the lav arm, install a santee looking out
for the revent at 42", a med 90 el can be used, and then tie back to the other vent using a santee turned upside down.
Prime and glue the PVC pipe.
They have kits at the hardware store with both cans.

Pick up a pvc p-trap with the trap adapter in the bag.
The trap can be a 1-1/2", it should come with a 1.5 slip joint and for the lav, a 1.5x1.25 reducing slip joint washer.
Use the reducing slip joint washer for the 1.-1/4" tailpiece.

Like This

I would cut the tee out. Since it appears the riser pipe is 2", I would then install a 2x1 1/2x1 1/2x1 1/2 "back to back fixture" fitting sideways AND a cleanout below it. Use a street ell into the right side and a length of pipe and elbow for the left one. The right hand drain will be "off center" but that is easily corrected with a fitting in the pipe between the wall and sink. You will have a proper drain with minimum cost and effort.

The thing that concerns me about the proposed diagram is that the wall is a load bearing wall and I am hesitant to cut 2" holes in two studs. Am I overly cautious?

I realize that it is much more trouble, but can I make the left lav plumbing essentially a mirror image of the right...running the left vent through the top plate and tying it into the right vent above the ceiling? Also, running the drain through the floor and again tying to the right drain below the floor?

Also, can I just run the supply lines off the right side as shown in the enclosed pic? Obviously this would mean that there is only one cutoff for both lavs. Advisable or not?

Thanks for the help
Jim

double up the load bearing studs

you've got lots of access and room to come up through the floor with a new drain and supplies. Hj's method is certainly cheaper (if you can get your hands on a double fixture fitting...that fitting is unheard of where I am and is special order) and faster, but you will have a tough time bringing that cold line around that 2" (?) drain stack. You've also got corrosion going on there on both risers...best to address that while you have the wall open.

Your studs are under compression, not torsion, so they will lose little strength by drilling them, but if you are concerned "stud shoes" will stiffen them at the openings. I have used TWO of them in 60 years of plumbing.