Adding second bathroom sink

[Jimmyc11]

Hello. First time poster. Remodeling bath that had a double sink vanity on a single drain. Wanting to do this right. What's a proper method to plumb drain/vent for second sink on right? Can I just tee off of existing inlet and run horizontal pipe to second sink (white line on pic)? AAV on second sink? I can cut into wall above if necessary and also I have access to plumbing in crawlspace. TIA

 

[Twowaxhack]

What’s that bright light in the pic ? I need to get one of those !

 

[Jimmyc11]

Pic without "light saber" graphic meant to indicate planned route of drain pipe to second sink.

 

[Twowaxhack]

Cut a 1.5” sanitary tee into this stack and keep it tight to the bottom of that outlet box, rising 1/4” per ft until you reach your destination 3-4 feet to your right. Use 1.5” trap.

No extra vent is needed. It’ll work perfect even if the plumbing code may or may not approve.

 

[Jimmyc11]

View attachment 44768
Cut a 1.5” sanitary tee into this stack and keep it tight to the bottom of that outlet box, rising 1/4” per ft until you reach your destination 3-4 feet to your right. Use 1.5” trap.

No extra vent is needed. It’ll work perfect even if the plumbing code may or may not approve.

Twowaxhack, thanks for the reply. I appreciate that it will be less work than I imagined. Previous owners had glued a 45 and a tee at the wall inlet and jury rigged a series of elbows and pipe actually drilled through the vanity. I had to cut it all out to get this far.

 

[Jimmyc11]

Original configuration.

 

[Twowaxhack]

View attachment 44769
Original configuration.

That was definitely not correct. They built a form of an S-trap.

 

[MicEd69]

The following is a code approved method for plumbing dual lavatory sinks.

 

[Twowaxhack]

The following is a code approved method for plumbing dual lavatory sinks.
View attachment 44770

Yes, that’s called a end outlet continuous waste. It’s typically done on double bowl kitchen sinks. Most double bowl vanity has drawers in the middle to pee all over that parade. I’d never chose to pipe this way if I had the wall already open.

The water piping would fail.

 

[MicEd69]

Yes, that’s called a end outlet continuous waste. It’s typically done on double bowl kitchen sinks. Most double bowl vanity has drawers in the middle to pee all over that parade. I’d never chose to pipe this way if I had the wall already open.

The water piping would fail.

I was only looking at the drain lines as that is what the original question was.

But yep, you are right, the water piping in that picture is a mess. But the drain plumbing in that picture is per code unlike your suggested drain plumbing. And yes, I know you can do whatever you want because you are a big deal in your town. But some of us still have to live in places where the AHJ is extremely strict when it comes to codes.

 

[Jimmyc11]

Since the previous owners had glued the whole mess together at the wall they certainly weren't concerned about any future work. I was surprised that it worked as well as it did. Honestly, both sinks were rarely used at the same time. And, when they were it wasn't heavy use. So, I knew I would be getting into the wall anyway so I was hoping to tidy things up. Going to re-route supply lines as well to gain back storage space and pretty it up.

 

[Twowaxhack]

I was only looking at the drain lines as that is what the original question was.

But yep, you are right, the water piping in that picture is a mess. But the drain plumbing in that picture is per code unlike your suggested drain plumbing. And yes, I know you can do whatever you want because you are a big deal in your town. But some of us still have to live in places where the AHJ is extremely strict when it comes to codes.

I’d fail your pic because it’s sagging in the middle.

I’d pass my suggestion because it works fine. Remodel work is typically not held to the same standard as new construction because you’re working with an existing structure and knowledgeable code officials with real plumbing installation experience understands what works and what doesn’t.

A guy could waste material, time and chop the structure up to add a revent but it wouldn’t be doing anything but satisfying some idiot with a badge and a code that whores itself out for money to the plumbing manufacturers. I wouldn’t waste the opportunity to explain that to any inspector that was willing to stand before me and argue different.

 

[Twowaxhack]

Some codes limit the distance of continuous wastes between the two fixtures outlets to no more than 30”.

This pic shows at least 32” apart because those pieces that they used are 16” each and two makes it 32”. And it’s sagging as a result.

So technically it may fail in some locations, if not most.



The same idiot that piped the drain also did the water so it’s no surprise it’s Fubar.

 

[MicEd69]

Some codes limit the distance of continuous wastes between the two fixtures outlets to no more than 30”.

This pic shows at least 32” apart because those pieces that they used are 16” each and two makes it 32”. And it’s sagging as a result.

So technically it may fail in some locations, if not most.

View attachment 44771

The same idiot that piped the drain also did the water so it’s no surprise it’s Fubar.

I was simply providing a picture of the basic layout of the drain plumbing. It was not an attempt at providing the actual fittings or details or dimensions.

But I must say, according to the scale I made using the spray head on the can in the lower left of the picture, the distance between the two sink drains is 29 3/16", or a full 13/16" less than the 30" maximum that some codes have.

Twowaxhack, you really need to lighten up a bit.

 

[Twowaxhack]

I was simply providing a picture of the basic layout of the drain plumbing. It was not an attempt at providing the actual fittings or details or dimensions.

But I must say, according to the scale I made using the spray head on the can in the lower left of the picture, the distance between the two sink drains is 29 3/16", or a full 13/16" less than the 30" maximum that some codes have.

Twowaxhack, you really need to lighten up a bit.

The measurement is made center of fixture to center of fixture. Not “ between the two drains “

Lighten up ? Read the thread again from top to bottom and then take your own advice.

 

[Twowaxhack]

If anyone is interested in wet venting and what will work and “ what will work but didn’t make it into the code book because it was lunch “ then read this.

https://forms.iapmo.org/email_marketing/codespotlight/Sept15.htm

Dr. Hunter probably spent $1,000,000 in 1950 to find out that 1.5” wet vents are fine.

 

[Ludington]

If anyone is interested in wet venting and what will work and “ what will work but didn’t make it into the code book because it was lunch “ then read this.

https://forms.iapmo.org/email_marketing/codespotlight/Sept15.htm

Dr. Hunter probably spent $1,000,000 in 1950 to find out that 1.5” wet vents are fine.

Oh, that makes my head hurt.... it's to early and havnt finished my coffee yet.

 

[MicEd69]

The measurement is made center of fixture to center of fixture. Not “ between the two drains “

Lighten up ? Read the thread again from top to bottom and then take your own advice.

Twowaxhack, you said, "It’ll work perfect even if the plumbing code may or may not approve."

I said, "The following is a code approved method for plumbing dual lavatory sinks."

Since the original question was about the drain piping for two sinks, the picture I posted was only meant to provide a general layout of the drains between the two sinks. And when I said, "between the two drains", I was talking about the distance between the center line of each sink's drain.

I remeasured that distance and it is more like 29 1/8" instead of 29 3/16".

So, yep, you really need to lighten up a bit and don't let your blood pressure rise to dangerous levels. Think about the kids for heaven's sake.

 

[Twowaxhack]

Twowaxhack, you said, "It’ll work perfect even if the plumbing code may or may not approve."

I said, "The following is a code approved method for plumbing dual lavatory sinks."

Since the original question was about the drain piping for two sinks, the picture I posted was only meant to provide a general layout of the drains between the two sinks. And when I said, "between the two drains", I was talking about the distance between the center line of each sink's drain.

I remeasured that distance and it is more like 29 1/8" instead of 29 3/16".

So, yep, you really need to lighten up a bit and don't let your blood pressure rise to dangerous levels. Think about the kids for heaven's sake.

So what. Take the info or leave it.

Piping lavatories like that is a dumb idea even if the code allows it 30” or less. Now, you can agree or disagree. The original poster can agree or disagree.

I don’t care today…….I’m busy with plumbing work. Now y’all have fun.

 

[waternwavs]

Newcomer to the forum, not a plumber but seasoned home inspector (please be kind and go easy on me
I did a search and found this post. Can one of you long time professionals chime in on this setup? I have ideas about what is going on in this bathroom double-sink setup but would rather hear it from you guys. Please take note of the 'T'-fittings out the back of each sink cabinet before commenting...