Single to Double Sink Vanity (again)

hj · May 29, 2011

quote; I cannot figure out whether or not Terry of "hj" are making sense either.
Too many assumptions, to be certain.
Too many vague terms.

That is because you do NOT know what you have now, do not know HOW to revise it, and may not have the ability to do either. A picture of the pipe coming out of the wall and one of the cabinet is absolutely useless to determine HOW, or WHAT, you have to do to make the new installation. And if someone says a "single trap is safer", then I would pretty much reject their advice because they do not either. In many cases posters will ask, "Why do I get a sewer gas smell when I turn on the water", and it is usually a buildup in the sink's overflow and the odor is pushed out when the faucet is opened. IF you use a single trap and a long continuous waste, you have MUCH LARGER area, than a sink overflow, to get a build up, THEREFORE, when you turn on the water in one sink that "fouled" air WILL be pushed out of the other sink into the room. So now you will know the reason for the odor and will not have to ask us where it comes from. The ground wire had BETTER be connected to the cold water pipe, and it is an unusual location for it. It is usually at the water heater.

Palmer · May 29, 2011

yikes...tough crowd here...i get it...i got it...

Sponsor · 2022-01-29T12:20:58-0800

benjm · Jul 10, 2011

Terry said:
If you can, that would be best.

Brand new here. I am also trying to convert a single vanity to a double but both the drain and vent pipes are to the left of where both vanities would be. What's the best way to do this? Can I just extend the single arm and just have 2 elbows on the same drain pipe? Thanks.

Ben

Jerome2877 · Jul 10, 2011

Brand new here. I am also trying to convert a single vanity to a double but both the drain and vent pipes are to the left of where both vanities would be. What's the best way to do this? Can I just extend the single arm and just have 2 elbows on the same drain pipe? Thanks.

No this will cause siphoning of the traps. Check out this thread.

https://terrylove.com/forums/showthread.php?34039-Single-to-double-vanity-better-way-Illinois

benjm · Jul 10, 2011

Jerome2877 said:
No this will cause siphoning of the traps. Check out this thread.

https://terrylove.com/forums/showthread.php?34039-Single-to-double-vanity-better-way-Illinois

Thanks, great information there. So I opened up the wall and here is what I see. I am a little confused as to why there is a main 2" drain and then another 1.5" just for the sink drain that goes under the house. The one on all the way to the left looks like the vent stack, the next one going out the other side of the wall is the washer drain. Both of the vanity sinks will be to the right of the existing one, 1ft and 5ft. Any ideas on the best way to do this? Much appreciated.

Terry · Jul 10, 2011

From left,
Toilet vent
Washer drain
Lav Drain

If I were to add a second lav, I would put a santee below the existing tee on the lav, extend over, long turn 90 up to a second santee looking out, and then revent into the existing 1.5" ABS

Take the shutoffs on your existing lav and throw those away. Those are not reusable.
Save yourself thousands in repairs later and spend $15 now.

benjm · Jul 10, 2011

Terry said:
From left,
Toilet vent
Washer drain
Lav Drain

If I were to add a second lav, I would put a santee below the existing tee on the lav, extend over, long turn 90 up to a second santee looking out, and then revent into the existing 1.5" ABS

Take the shutoffs on your existing lav and throw those away. Those are not reusable.
Save yourself thousands in repairs later and spend $15 now.

Yes, I've already bought new shutoffs. Thanks. Is this what you mean in black? I also want to move the existing lav drain over 1' to the right (in red). Is it ok to have them both on the same arm?

Terry · Jul 10, 2011

Well, my instructions were to place a tee below the other tee, run to the rigth and the 90 up for the next tee.

My inspector here would want that. You're on the West Coast, not the East Coast.
Best to do it the way we do it here.

benjm · Jul 10, 2011

Isn't where the black and red pipes meet what you are referring to as below the tee on the lav? I apologize if I misunderstood you, I'm a newbie and still trying to learn all the terms.

Plumber2011 · Jul 11, 2011

Hi Benjm...

I'm pretty sure this is what Terry was talking about (see image). You are best to simply stub the sanitary tee straight out for the sink on the right.

benjm · Jul 11, 2011

plumber2011 said:
Hi Benjm...

I'm pretty sure this is what Terry was talking about (see image). You are best to simply stub the sanitary tee straight out for the sink on the right.

Got it. Trying to do this as simply as possible. Is there any down side to just elbow out the current lav drain to go in the middle of where the double vanity would be and the run a split after the p-trap 2ft each side?

Also, since the supply lines go out on both sides of the wall and essentially crosses the drain pipe, how would I tee out the supplies to the extra sink?

Thanks for all your input!

jwest · Feb 2, 2015

Terry said:
One more way to do it if you only have 1.5 pipe in the wall.
Not UPC code, but not bad either.
Normally you would have 2" on the lower end, and use a fixture cross.

Sorry to hijack an old thread (first time user here), but I had a question about why the above is not code. I am curious because I have read of maintenance issues using the double fitting shown below. That is, I read that it can be difficult to snake because the snake jumps across to the other lav. Or could this be referring to the difference between a double sanitary T vs a double wye? The reason I ask is if snaking is a problem with the double wye (as well as the double T), then the above solution (green background) seems like a very effective way to avoid that issue. I am just curious how it is against code since it seems to be great for avoiding the maintenance issue.

Thanks,
Jerry

hj · Feb 2, 2015

Geniescience: quote; It's safer to have only one P trap for the two sinks, so that would be a continuous waste kit

If that is the extent of your plumbing expertise, go back to being a homeowner. One "P" trap is NOT "safer" than two and continuous waste kit is a good HANDYMAN way to do it, but he is NOT asking for handyman advice, because if he were he would NOT be at this site. I do not "see" a grounding wire, but if there is one attached to the hot water line, that is a good way to "destroy" your water heater and have a premature failure due to leaking.

CaliforiaBoy · Mar 26, 2016

jwest said:
Sorry to hijack an old thread (first time user here), but I had a question about why the above is not code. I am curious because I have read of maintenance issues using the double fitting shown below. That is, I read that it can be difficult to snake because the snake jumps across to the other lav. Or could this be referring to the difference between a double sanitary T vs a double wye? The reason I ask is if snaking is a problem with the double wye (as well as the double T), then the above solution (green background) seems like a very effective way to avoid that issue. I am just curious how it is against code since it seems to be great for avoiding the maintenance issue.

Thanks,
Jerry

Hi,
I am in California, San Jose. I see on this picture that more then two consecutive studs have been drilled. Bored Holes in 2x4 Studs: "60%* allowed in any non-bearing wall or in bearing walls with not more than two successive studs bored and doubled". Here, on this picture we have three consecutive studs drilled, is that allowed, Is that per code? I'm asking because I have similar situation and don't know how do it. My wall is non bearing interior wall. Thank you.

24SevnLibrarian · Oct 15, 2016

I have to agree with Palmer's statement about the replies from the experts on this forum. I have been fortunate enough to locate multiple online forums where I could ask for help with DIY repairs whether it be construction, furniture repair, car issues, etc. and while one initial response I received on another forum was slightly sarcastic and defensive, some of what I have read here makes me question why the forum exists. People asking for help typically don't mean to question your authority. When they ask whether something can or cannot work, it is because they do not understand not being trained professionals in the industry. By providing the opportunity for people to ask questions, I hope you see it as the chance not only to offer advice but also to help non-professionals solve their problems while educating them on why it is done a certain way.
Not all posters will be at your intelligence level, have common sense or able to grasp what you mean. However, most of the time, they genuinely want to understand how something works, and it may be a steep learning curve for them. Otherwise,they would probably choose to hire someone to solve the problem.
I joined this forum because I had been reading information on other sites to learn about sewer gas odors coming from bathroom pipes in an older home where I am replacing the vanity, sink, and faucet. Luckily, another site explained in layman's terms how a p-trap works and I was able to understand most of the experts' responses here. However, the insults and sarcasm directed at people who want to understand and have a conversation about how to solve plumbing problems was unnecessary. I know it is difficult to bring complex issues down to a basic level and I get that there are times when untrained DIYer's may come across as if they think they know more than the pros when they have no clue. However, being ignorant does not mean someone is incapable of understanding when something is explained well.
While I am not an expert and will be the first to admit plumbing is not what I do best, I appreciate it when others are willing to patiently excuse my ignorance and mistakes and help me learn to perform tasks safely and correctly so they are done right the first time.

Terry · Oct 16, 2016

I also enjoy going to comedy shows. Not everybody does. The plumbers taking their time here have devoted thousands of hours to educating and providing workable answers. Sometimes we're having fun and sometimes we're trying to beat the correct answer in so that the homeowner can do the work and have a happy plumbing inspector when it's all done. We are also worried about protecting water safety. To us in the plumbing field, that is the goal.
In the plumbing world, especially those of us that have been doing the work for decades, our classroom was crawling through mud with our coworkers insulting us to see how tough we were. They weren't going to waste their time on us if we were quitters.
I would like to think that the people that come here to learn, are also not quitters in life, and are tough enough to discuss and share ideas with those that have been through fire.

24SevnLibrarian · Oct 17, 2016

SAS said:
Not sure if you were trying to make a joke or just be confrontational. I know that the plumbing "goes in the wall" and obviously if there is a single sink there now, there is a waste pipe that goes into the wall. What I was asking was whether it was necessary to open the wall to determine where/how the plumbing is routed in the wall (as suggested by HJ), or whether I could simply use the existing waste pipe and hook the two sinks to that pipe. And if I can use that existing pipe, what is the best way to hook the two sinks together and up to that pipe?

If you can help answering those questions, that would be great. If not, I'm not sure why you bothered posting a reply.

Terry · Oct 18, 2016

I believe we tried to explain that yes, the wall gets opened, and plumbing two lavs on the outside wasn't the right thing to do.
Why is that so hard to understand?
Yes. There are sites out there that will confirm anything and any way you want to do things. This is not one of those sites. When homeowners ask the plumbers what is right, we try to give them the correct information.
If you don't care about correctness, you might as well ask someone that has never plumbed, and you can get the answer you want. It won't be a good answer, but you can feel smart about yourself and pat yourself on the back.
We do provide a service to those that "do" want to know the right way. And that's how it's going to be.

ironnickwhite · Nov 10, 2016

what about when the wall cannot be opened? i have a single sink with the cast iron drain and vent in a vertical channel in an exterior brick wall. it's directly behind the current sink. new sink needs to be 30" down the wall to the right. from what i've read here so far, perhaps this isn't a possibility? thanks for any help you can provide.

Terry · Nov 10, 2016

ironnickwhite said:
what about when the wall cannot be opened? i have a single sink with the cast iron drain and vent in a vertical channel in an exterior brick wall. it's directly behind the current sink. new sink needs to be 30" down the wall to the right. from what i've read here so far, perhaps this isn't a possibility? thanks for any help you can provide.

You can tee below, come out of the wall, and run to the other lav. I would then add a AAV to prevent the trap siphoning. I will be adding an AAV to a lav tomorrow. They did something similar, but in the wall, coming up with a 90 bend before hitting the p-trap. There is a godawful smell coming from that lav.

Single to Double Sink Vanity (again)

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