Converting single sink to double sink

[KiviP]

Hi everyone,
I am planning on converting the bathroom vanity to a double sink during our bathroom remodel.
Mu question is regarding the setup I have in mind.
This is what I have

I am planning on cutting into the pipe above and below the trap arm indicated by the red line (shown below). Pipes are 1.5 steel. Now would it be ok to use a double sanitary tee or should i use a double wye (marked as 1)

I am planning on using two 45s on the bends to the trap adaptors on each run (indicated by 2 and 3).
Last, pipe goes between the studs and I dont want to cut into them. I am planning on offsetting them and bringing them by usinc the 45s so they come out of the studs bays and into the open space. Is this a reasonable design?

 

[wwhitney]

Minnesota uses the UPC, so your horizontal 1.5" drain to the stack is limited to one sink. For two sinks, you'll need to upsize the drain to 2" all the way to the stack.

Cheers, Wayne

 

[Sponsor]

 

[KiviP]

@wwhitney Thanks a lot for mentioning this. I totally forgot about that...
So the steel vent pipe is 2 inches and it goes down to 1.5 inch. The drain itself is 1.5.
What they did originally back in the 50s was to join steel with some lead pipes of the same size. I traced the lead pipe and it goes into a 2 inch cast iron pipe. I can cut down right after the hub and put a banded shield and go to ABS/PVC. Assuming I correct the vent and drain line size, is the setup I have correct? And I assume a sanitary tee for two drain lines going to a vertial pipe is correct, or do I need a double wye?

 

[wwhitney]

I traced the lead pipe and it goes into a 2 inch cast iron pipe. I can cut down right after the hub and put a banded shield and go to ABS/PVC.

Sure. [Where you say "lead pipe" I assume you mean galvanized.] Or you can remove the galvanized from the hub and get a rubber donut to join new 2" ABS into the hub. But as the galvanized is presumably leaded into the cast iron hub, your idea is probably simpler.

Assuming I correct the vent and drain line size, is the setup I have correct? And I assume a sanitary tee for two drain lines going to a vertial pipe is correct, or do I need a double wye?

I didn't really follow your description of the arrows at 2 and 3. But just looking at your drawing as an elevation, at the crossing point you want to use a 2x1.5x1.5x1.5 double fixture fitting. That's a fitting shape that is intermediate between a double sanitary tee and a double wye. The top of the fitting profile is like the double sanitary tee, which you need for venting the two trap arms, and the bottom of the fitting profile is closer to a double wye, which helps with the drainage.

If you have trouble finding the 2x1.5x1.5x1.5 fitting, you could use a 2" fitting with 2x1.5 reducer bushing. And of course the vent can be 2" if that's simpler, but only a 1.5" vent is required.

If you use the double fixture fitting, and then follow the normal rules for trap arms, the installation shown complies with the UPC. I hear it can be hard to snake through a double fixture fitting rather than skipping across, so adding a cleanout below the double fixture fitting could be useful in the future.

Cheers, Wayne

 

[KiviP]

Sure. [Where you say "lead pipe" I assume you mean galvanized.] Or you can remove the galvanized from the hub and get a rubber donut to join new 2" ABS into the hub. But as the galvanized is presumably leaded into the cast iron hub, your idea is probably simpler.

I didn't really follow your description of the arrows at 2 and 3. But just looking at your drawing as an elevation, at the crossing point you want to use a 2x1.5x1.5x1.5 double fixture fitting. That's a fitting shape that is intermediate between a double sanitary tee and a double wye. The top of the fitting profile is like the double sanitary tee, which you need for venting the two trap arms, and the bottom of the fitting profile is closer to a double wye, which helps with the drainage.

If you have trouble finding the 2x1.5x1.5x1.5 fitting, you could use a 2" fitting with 2x1.5 reducer bushing. And of course the vent can be 2" if that's simpler, but only a 1.5" vent is required.

If you use the double fixture fitting, and then follow the normal rules for trap arms, the installation shown complies with the UPC. I hear it can be hard to snake through a double fixture fitting rather than skipping across, so adding a cleanout below the double fixture fitting could be useful in the future.

Cheers, Wayne

Thanks! So the 'lead pipe' I mentioned is like a steel pipe but it has been bent to conform to the turns they needed. Unlike the steel pipe, it is continuous and is one run from the trap adapter to the case iron pipe. It has then been leaded into the cast iron hub.

As for 2 and 3, all I meant was using a long 90 vs to 45s to make the turn from the arm towards the double fixture connection.

I think it might be easier to find the 2 inch double fixture and just use reducers, but I can get to that piece when I take things out.

 

[wwhitney]

Thanks! So the 'lead pipe' I mentioned is like a steel pipe but it has been bent to conform to the turns they needed. Unlike the steel pipe, it is continuous and is one run from the trap adapter to the case iron pipe. It has then been leaded into the cast iron hub.

So maybe it is lead, that's beyond my experience.

As for 2 and 3, all I meant was using a long 90 vs to 45s to make the turn from the arm towards the double fixture connection.

Either a LT90 or two 45s is fine. It's common to use a 1-1/2" quarter bend, so that the bend doesn't stick out of the wall, but I think that's technically not allowed by the UPC. Two 45s would stick out even more than a LT90.

Cheers, Wayne

 

[KiviP]

So maybe it is lead, that's beyond my experience.

Either a LT90 or two 45s is fine. It's common to use a 1-1/2" quarter bend, so that the bend doesn't stick out of the wall, but I think that's technically not allowed by the UPC. Two 45s would stick out even more than a LT90.

Cheers, Wayne

Thanks! Ans lastly, can this double tee be used? NIBCO® Hub ABS DWV Double Tee at Menards https://www.menards.com/main/plumbi...double-tee/i27045c/p-1444449190860-c-8562.htm

 

[wwhitney]

Thanks! Ans lastly, can this double tee be used? NIBCO® Hub ABS DWV Double Tee at Menards https://www.menards.com/main/plumbi...double-tee/i27045c/p-1444449190860-c-8562.htm

No, as I said you need a double fixture fitting rather than a double san-tee. E.g.

NIBCO® 2" x 1-1/2" x 1-1/2" x 1-1/2" Hub DWV PVC Double Fixture Tee

The NIBCO® PVC DWV double fixture tee is used in. Residential and Commercial drain, waste, and vent systems. The PVC DWV double fixture tee features all hub connections and allows for a connection to be made in. continuous pipeline and branch out to a different direction. Please refer to NIBCO®...

www.menards.com

Although that's in PVC; I'm not finding it on menards.com in ABS, so you may have to look elsewhere if you need ABS. E.g.

https://www.supplyhouse.com/Nibco-I277570-2-x-2-x-1-1-2-x-1-1-2-H-x-H-x-H-ABS-Double-Fixture-Tee-5835BR

Cheers, Wayne

 

[KiviP]

No, as I said you need a double fixture fitting rather than a double san-tee. E.g.

NIBCO® 2" x 1-1/2" x 1-1/2" x 1-1/2" Hub DWV PVC Double Fixture Tee

The NIBCO® PVC DWV double fixture tee is used in. Residential and Commercial drain, waste, and vent systems. The PVC DWV double fixture tee features all hub connections and allows for a connection to be made in. continuous pipeline and branch out to a different direction. Please refer to NIBCO®...

www.menards.com

Although that's in PVC; I'm not finding it on menards.com in ABS, so you may have to look elsewhere if you need ABS. E.g.

https://www.supplyhouse.com/Nibco-I277570-2-x-2-x-1-1-2-x-1-1-2-H-x-H-x-H-ABS-Double-Fixture-Tee-5835BR

Cheers, Wayne

Thanks Wayne. SupplyHouse works great and I order from them. Thanks for all the help!

 

[KiviP]

@wwhitney Hey Wayne, sorry to bug you but here is another think I was considering. The vent branch for the the current vanity sits around 38 inches which is roughly 6 inches above the floor rim (need to check again but if I recall correctly the current vanity sits at 30 inches). Our vanity is pretty low. We want to install the new one a bit higher but it will make the vent to be lower than the 6" minimum. Here is what we have.

Now I was wondering if it legal to add a wye that is angled at least 45 degrees with another 45 bend to raise the vent branch a bit. That can give me 4-5 inches of rise, but then again this vent branch is not going into the main stack so I am wondering if that is allowed. The rest I updated to match what you suggested

This is the actual setup again

 

[wwhitney]

No, all of your dry vents need to be pitched back towards the drain they serve at 1/4" per foot. [That's a UPC requirement; I think the IPC just requires they be pitched to a drain, not necessarily the drain served. MN uses the UPC.]

That's probably more important than whether they are 6" or 4" above the fixture flood rim. Obviously the correct solution is to raise all the horizontal vents and raise the connection point at the stack. Which it looks like you have access to.

Cheers, Wayne

 

[KiviP]

No, all of your dry vents need to be pitched back towards the drain they serve at 1/4" per foot. [That's a UPC requirement; I think the IPC just requires they be pitched to a drain, not necessarily the drain served. MN uses the UPC.]

That's probably more important than whether they are 6" or 4" above the fixture flood rim. Obviously the correct solution is to raise all the horizontal vents and raise the connection point at the stack. Which it looks like you have access to.

Cheers, Wayne

Got it. So the 1st issue with my approach is that I am not pitching toward the sink drain and going back to the vent branch. 2nd issue is that even if I do that and pitch towards my drain, im creating a hump by elevating and then dropping. Right? Is that similar to an S vent issue? Just visualizing

 

[wwhitney]

Got it. So the 1st issue with my approach is that I am not pitching toward the sink drain and going back to the vent branch. 2nd issue is that even if I do that and pitch towards my drain, im creating a hump by elevating and then dropping. Right? Is that similar to an S vent issue? Just visualizing

The main issue with your latest drawing, UPC wise, is that left most red segment which is pitched towards the 2" black vent, rather than towards the lav drains.

There's no performance issue in regular use with the arrangement you propose. And the IPC would allow it, as it just requires each dry vent to be pitched to some drain, not the drain being vented. So it's nothing like an S vent, it's not going to cause your traps to siphon or anything.

Basically, I'm unsure why the UPC has that provision. Here's the reference, in case it helps:

Chapter 9 Vents: Vents, Maine Plumbing Code 2021 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Cheers, Wayne

 

[KiviP]

The main issue with your latest drawing, UPC wise, is that left most red segment which is pitched towards the 2" black vent, rather than towards the lav drains.

There's no performance issue in regular use with the arrangement you propose. And the IPC would allow it, as it just requires each dry vent to be pitched to some drain, not the drain being vented. So it's nothing like an S vent, it's not going to cause your traps to siphon or anything.

Basically, I'm unsure why the UPC has that provision. Here's the reference, in case it helps:

Chapter 9 Vents: Vents, Maine Plumbing Code 2021 | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

Cheers, Wayne

So is the issue under UPC the wye that causes the elevation. What if I branch of with the wye but it pitches towards the double fixture?

 

[wwhitney]

So is the issue under UPC the wye that causes the elevation. What if I branch of with the wye but it pitches towards the double fixture?

Not 100% sure I'm following, but I don't see how that helps you. If the black horizontal (existing) vent is less than 6" above the flood rim level of the sink, there's no way to simultaneously comply with the 6" above flood rim rule and the pitches back towards the fixture rule.

Cheers, Wayne

 

[John Gayewski]

No, all of your dry vents need to be pitched back towards the drain they serve at 1/4" per foot. [That's a UPC requirement; I think the IPC just requires they be pitched to a drain, not necessarily the drain served. MN uses the UPC.]

That's probably more important than whether they are 6" or 4" above the fixture flood rim. Obviously the correct solution is to raise all the horizontal vents and raise the connection point at the stack. Which it looks like you have access to.

Cheers, Wayne

I'm going from memory but I'm pretty sure vents can be level or pitched back toward the drain they serve.

 

[wwhitney]

I'm going from memory but I'm pretty sure vents can be level or pitched back toward the drain they serve.

Yes, UPC does allow level (although IPC doesn't), thanks for the correction. Does help the OP with the existing horizontal vent that's too low if he raises the lavs, though.

Cheers, Wayne

 

[KiviP]

Not 100% sure I'm following, but I don't see how that helps you. If the black horizontal (existing) vent is less than 6" above the flood rim level of the sink, there's no way to simultaneously comply with the 6" above flood rim rule and the pitches back towards the fixture rule.

Cheers, Wayne

I am dumb. Did not get enough sleep. You are right because the main 2 inch vent branch will be below 6 inch and that whole branch needs to be 6 inch above the highest fixture it serves which is the lav...