Connecting Sink Drain before the toilet vent?

Users who are viewing this thread

megaboy1

New Member
Messages
8
Reaction score
0
Points
1
Location
Toronto, Ontario
Hi guys, DIY plumbing question.


2nd floor, I'm moving a double vanity next to a toilet.

Is this an okay application to connect the sink drain before the toilet vent like the image ?

The sink will have a AAV venting, or can I share the toilet vent?


64hwxmdZ_o.jpg


Thank you for your inputs!
 

wwhitney

In the Trades
Messages
7,036
Reaction score
1,990
Points
113
Location
Berkeley, CA
So, you'd need to check your plumbing code; which plumbing code is applicable to the project?

By connecting the lav drain between the closet flange and the dry vent for the WC, you are effectively make the lav drain the wet vent for the WC. In the US, that would mean that the drain carrying the double lavs would have to be 2" since it is acting as a wet vent and carrying 2 DFUs. One of the US plumbing codes would further require that the double lavs has a 2" dry vent through the roof, as it doesn't allow AAVs; the other allows AAVs, and any vent piping between the lav takeoff and the AAV could be 1-1/2".

Cheers, Wayne
 

Reach4

Well-Known Member
Messages
40,480
Reaction score
4,791
Points
113
Location
IL
Must vent the lavatory. I am not sure what fitting you are representing. If that is a wye bringing in the lavatory drainage to meet the toilet drainage, that is fine. You may not need the 3 inch vent as long as there is a thru the roof vent elsewhere in the system. But that vent certainly will not hurt.

I think in Ontario code, the AAV must be 6 inches or more above the flood level of the lavatory.
 

megaboy1

New Member
Messages
8
Reaction score
0
Points
1
Location
Toronto, Ontario
By connecting the lav drain between the closet flange and the dry vent for the WC, you are effectively make the lav drain the wet vent for the WC.
Sorry guys, I have been away. Is there a disadvantage making WC vent through AAC? If there is, I can make the connection after the 3" main stack.(although much harder to achieve) Will that make the lav vent through the main stack as well? And I don't need AAC?
 

wwhitney

In the Trades
Messages
7,036
Reaction score
1,990
Points
113
Location
Berkeley, CA
Sorry guys, I have been away. Is there a disadvantage making WC vent through AAC?
No. Note that your double lav drain and your WC drain should connect via a horizontal (2% slope on inlets) wye; looking at the drawing in the OP again, that detail is not shown.

Will that make the lav vent through the main stack as well? And I don't need AAC?
Definite no. Every trap (not WCs) needs to be vented with one trap diameter of its outlet elevation to avoid the possibility of siphoning.

[The exception is something called "combination waste and vent" which some plumbing codes allow; you can check if your does, but I expect it would require the 3" stack serving as the vent to be connected between the two upstream most fixtures, i.e. between the two lavs.]

Cheers, Wayne
 

megaboy1

New Member
Messages
8
Reaction score
0
Points
1
Location
Toronto, Ontario
No. Note that your double lav drain and your WC drain should connect via a horizontal (2% slope on inlets) wye; looking at the drawing in the OP again, that detail is not shown.
Thank you Wayne.
As a novice, I had to spend some days searching and studying to really understand what you mean.
Now I think I understand some basic. I'm gonna use 2" pipes as it's wet venting, but not sure if I can achieve 2% slope. Will it be bad if I do 1/8" per foot?
And how much should I roll the 3x2 from horizontal position? Should I replace the * elbow with long sweep?
I'm gonna loosen the toilet flange bolts and rotate the pipe after cutting to get the clearance to fit the new 3X2. Hope that's okay.
And please let me know if you see any fault in the diagram.

plumb3.jpg
 

wwhitney

In the Trades
Messages
7,036
Reaction score
1,990
Points
113
Location
Berkeley, CA
1) Yes, a 2" pipe requires a 1/4" per foot slope.
2) Not at all. That is, both inlets of the 3x3x2 wye should be at 2% slope.
3) Yes, the elbow labeled star needs to be a LT90.
4) In your diagram, the san-tee above the elbow labeled star, that needs a 2" outlet. It can have a 1-1/2" side inlet, and all the sink drainage upstream of it can be 1-1/2". As to the top inlet (vent connection), the US code that allows AAVs would permit that to be 1-1/2". The other US code would require that to be a 2" vent through the roof.

You should check your Ontario plumbing code to see how it differs. Probably not on the first 3 points, but likely on the details in the last point.

Cheers, Wayne
 

megaboy1

New Member
Messages
8
Reaction score
0
Points
1
Location
Toronto, Ontario
1) Yes, a 2" pipe requires a 1/4" per foot slope.
Got it. guess that's a must. I will try.

2) Not at all. That is, both inlets of the 3x3x2 wye should be at 2% slope.
Not at all to roll the 3x2, right? I will just keep it flat only maintaining the 2% slope.
3) Yes, the elbow labeled star needs to be a LT90.
Got it. I will use a long turn elbow for that elbow. Guessing the ones above the stared one are fine with regular 90s.
4) In your diagram, the san-tee above the elbow labeled star, that needs a 2" outlet. It can have a 1-1/2" side inlet, and all the sink drainage upstream of it can be 1-1/2". As to the top inlet (vent connection), the US code that allows AAVs would permit that to be 1-1/2".
Oh, I was gonna use 2" for all the pipes. Guess AAV is not allowed to be connected to 2"? So then I will use a Reducing Coupling just above the san-tee and feed that 1-1/2" pipe to the AAV.
Hope that's how it's done.
 

wwhitney

In the Trades
Messages
7,036
Reaction score
1,990
Points
113
Location
Berkeley, CA
Guess AAV is not allowed to be connected to 2"?
No, it's fine to use a 2" vent, it would just be odd to have a 2" trap arm for a sink, unless the sink came with a 2" tailpiece already, which would be unusual.

Cheers, Wayne
 

megaboy1

New Member
Messages
8
Reaction score
0
Points
1
Location
Toronto, Ontario
No, it's fine to use a 2" vent, it would just be odd to have a 2" trap arm for a sink, unless the sink came with a 2" tailpiece already, which would be unusual.

Cheers, Wayne
Ah, good point! Oh, and the regular elbow (instead of LT90) below the sink 1 is fine because it's above the p-trap?
 

wwhitney

In the Trades
Messages
7,036
Reaction score
1,990
Points
113
Location
Berkeley, CA
the regular elbow (instead of LT90) below the sink 1 is fine because it's above the p-trap?
Generally that part of the piping would be tubular, rather than Schedule 40, and I'm not aware of different types of 90 degree elbows in tubular.

Cheers, Wayne
 

megaboy1

New Member
Messages
8
Reaction score
0
Points
1
Location
Toronto, Ontario
Generally that part of the piping would be tubular, rather than Schedule 40, and I'm not aware of different types of 90 degree elbows in tubular.

Cheers, Wayne
I tried my best google-fu, but I still have no idea what that means. I will just use a regular elbow for that one.
Thanks a lot Wayne. You saved me a lot of headaches. God bless.
 

wwhitney

In the Trades
Messages
7,036
Reaction score
1,990
Points
113
Location
Berkeley, CA
1-1/2" tubular pipe is 1-1/2" OD and thin wall, and the joints are slip joints. You can mix plastic and brass as you like.

1-1/2" Schedule 40 pipe is 1.9" OD, and greater than 1-1/2" ID. Plastic pipe is solvent welded. A "trap adapter" glues on to provide a slip joint connection to tubular pipe.

Cheers, Wayne
 

megaboy1

New Member
Messages
8
Reaction score
0
Points
1
Location
Toronto, Ontario
1-1/2" tubular pipe is 1-1/2" OD and thin wall, and the joints are slip joints. You can mix plastic and brass as you like.

1-1/2" Schedule 40 pipe is 1.9" OD, and greater than 1-1/2" ID. Plastic pipe is solvent welded. A "trap adapter" glues on to provide a slip joint connection to tubular pipe.

Cheers, Wayne
Ah, so tubular is the ones that have the slip and screw-tight type that I see under sinks. It would be weird to have a long turn inside cabinets as well. Another knowledge acquired. Thanks!
 
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