Do I need a vent for this config or any better ways to plumb this?

[Chulapol]

I'll try my best to describe my question. Please let me know if you need any clarification.

This is for my basement. I would like to install a bathroom sink and a bar sink. Each will be on the other side of a wall. The plumbing will be inside the wall. Based on the location of the existing drain rough-in, both sinks would have to share a horizontal pipe to connect the drain/vent. I attached a drawing as a reference.

1. Is it okay to do 90 degree from p-trap to another horizontal pipe (less than 6' from drain) and then vertical drain pipe?
2. If that's okay, what about if there are 2 p-traps? Do I need an additional vent or should each have its own individual vent?
3. Any suggestions or recommendations will be appreciated. The vertical drain is close to concrete wall that's why both sinks have to be on the same side of the drain.

 

[wwhitney]

First, to use that vertical drain in your basement as your dry vent, there needs to be nothing draining down from above. Is that the case?

If not, and your jurisdiction allows an AAV (the IPC does), you could use that instead for your vent. Otherwise, you have to get a dry vent from the basement up to a location where you have an existing dry vent.

If the vertical pipe is a dry vent, then on to your question. Conventionally you would have a dry vent on the first fixture drain before the second sink joins in, as in your second drawing. Then the second fixture is wet vented.

However, the IPC does allow two fixture drains to join and then be "common vented." Each trap arm must individually comply with the distance and drop requirements, which is a maximum 1-1/2" fall from trap to vent.

Cheers, Wayne

 

[Sponsor]

 

[Chulapol]

First, to use that vertical drain in your basement as your dry vent, there needs to be nothing draining down from above. Is that the case?

If not, and your jurisdiction allows an AAV (the IPC does), you could use that instead for your vent. Otherwise, you have to get a dry vent from the basement up to a location where you have an existing dry vent.

If the vertical pipe is a dry vent, then on to your question. Conventionally you would have a dry vent on the first fixture drain before the second sink joins in, as in your second drawing. Then the second fixture is wet vented.

However, the IPC does allow two fixture drains to join and then be "common vented." Each trap arm must individually comply with the distance and drop requirements, which is a maximum 1-1/2" fall from trap to vent.

Cheers, Wayne

Thank you for information. Mine is a dry vent. It goes directly to the roof. It was installed as part of our basement rough-in. As of right now, I plan to install individual vent for each drain. Do you think it's unnecessary or over killed? Attached is what I plan to do. The dry vent (blue) is 2" pipe. The drainage and individual vent pipes are 1 1/2". Each santi will be 18" above the floor. The individual vents will go up to about 45" from the floor. Does the distance between two drain matter? They will be quite close.

 

[wwhitney]

The configuration shown in your photo is fine, with the height of 45" OK if that is at least 6" above the fixture flood rim. The upper elbow on the right can be a quarter bend, and the upper combo for combining vents can be a san-tee (since all connections are vents). The blue segment on the left between san-tees is not actually required--you could replace both san-tees with quarter bends.

Cheers, Wayne

 

[Chulapol]

The configuration shown in your photo is fine, with the height of 45" OK if that is at least 6" above the fixture flood rim. The upper elbow on the right can be a quarter bend, and the upper combo for combining vents can be a san-tee (since all connections are vents). The blue segment on the left between san-tees is not actually required--you could replace both san-tees with quarter bends.

Cheers, Wayne

Thank you very much for your insights. I was thinking of 45" b/c I figure that the sink is probably 36" high. You are right about the blue section between san-tees. Now I can see that it's not necessary since it's a dry vent. Just to confirm, from my new attachment, (1) would a quarter bend; (2) would be a san-tee; and (3) & (4) would be quarter bends. Also to verify, as for (4), since it's drain line, is it ok for it to be a quarter bend or should it be a long sweep 90? I remember people call a quarter bend "vent 90" and thought it is meant for a vent only.

 

[wwhitney]

On 1-4, yes.

For drainage: quarter bend if the outlet is vertical. LT90 if the outlet is horizontal.

A vent 90 is tighter than a quarter bend--the hubs are actually touching each other. It can only be used for venting.

Cheers, Wayne

 

[Chulapol]

On 1-4, yes.

For drainage: quarter bend if the outlet is vertical. LT90 if the outlet is horizontal.

A vent 90 is tighter than a quarter bend--the hubs are actually touching each other. It can only be used for venting.

Cheers, Wayne

sorry to bother with additional questions. In an attempt to reduce # of fittings, I thought of another way and I'm not sure if it would work. Is it ok to stack san-tees and have drain coming from the same direction (see picture)? The blue is a dry vent (2"). The green is 1.5". If I can stack santees, then would any of these drains need individual vent? Appreciate your thoughts.

 

[wwhitney]

You can stack san-tees as on the left, and use a horizontal LT90 (or in this case a horizontal quarter bend is allowed) to bring each trap arm out of the wall. The trap arms end up at different heights (the difference can be minimized by using a street san-tee on top). Each trap arm (from trap to san-tee) has to have a total fall of no more than one pipe diameter. And the stack on the left will vent both sinks (dry venting the top one, which wet vents the bottom one).

But if you stack san-tees and then want to have one drain poke out of the wall (significantly) higher up than its san-tee at the stack, as the two fittings on the right suggest, then you must vent that separately and can bring the vent back to the stack at an elevation at least 6" above both flood rims. Because again the vent has to come off before the drain falls more than one pipe diameter.

Cheers, Wayne

 

[Chulapol]

Sounds like it would be okay to stack two san-tees on the left. Thank you for catching the san-tee on the right. I actually meant to use a horizontal bend to go out of the wall (not san-tee as I don't plan to add individual vent). I made another picture and with more details information. Let me know what you think.

Background: this will be a rough-in that will only have a drain stub out at 18" level for two sinks (Lavatory and small kitchen sinks). The picture is what will be inside a wall before adding stub-outs
Rough In Dimension: Plan to have a stub out at 18" +/- 1"
Blue Vent: 2"
Green Drain Lines: 1 1/2"
90 Bend: will all be quarter bend since it's smaller than 2" (according to IPC 2018)

(1) will be a drain for a small kitchen sink going out to one side of a wall. I will use a (horizontal to horizontal) quarter ben to go out. A p-trap for a kitchen sink will be 1 1/2"

(2) will be a drain for a lavatory sink going out to the other side of a wall. The drain line from the vent on the left will be about 6" +/- below the (1) drain line. I will then use a (vertical to horizontal) quarter bend to bring it up to the same 18" level and then use another (horizontal to horizontal) quarter bend to go out. Out there, for a lavatory sink, I plan to use a reducer to install 1 1/4 p-trap.

Does this sound ok?

 

[wwhitney]

(2) will be a drain for a lavatory sink going out to the other side of a wall. The drain line from the vent on the left will be about 6" +/- below the (1) drain line. I will then use a (vertical to horizontal) quarter bend to bring it up to the same 18" level and then use another (horizontal to horizontal) quarter bend to go out. Out there, for a lavatory sink, I plan to use a reducer to install 1 1/4 p-trap.

Does this sound ok?

No. Please reread my last post, it covers this case, what is wrong with the above, and what you need to do instead.

Cheers, Wayne

 

[Chulapol]

Because again the vent has to come off before the drain falls more than one pipe diameter.

Thanks for your patience and a quick feedback. Bare with me as I'm trying to understand this. This is the part I had to read and re-read numerous time and I think I now understand it. So if I understand correctly, if there were no drop to (2) drain [no 90 vertical 90 bend], it would not need an individual vent, correct?

So if I adjusted a few things
a. Changing a stub-out for a small kitchen sink [shallow sink] (1) to be at 24"
b. Changing a stub-out for a lavatory sink (2) to be at 18"
c. Installing stack san tee at 24" (1) and 18" (2) respectively.
c. As a result, there would be no drop for (2).

Would this work? Really appreciate your expertise.

 

[wwhitney]

Yes, and yes.

But while an 18" AFF (above finish floor) stub-out is reasonable for a lav (IIRC), 24" AFF for the kitchen sink stub-out is way too high. Go below the lav, not above the lav.

Or search this forum for a thread on suggested sink stub out heights, it comes up frequently.

Cheers, Wayne

 

[Chulapol]

That's great! Sounds like I'm getting close to a solution. Just curiosity though, is the main reason that kitchen sink drain should be below lav drain because of the drain fixture unit (dfu); sink = 2 & lav = 1?

So, if I swap them, would it be ok for lav drain to be at ~22" and kitchen sink at 16"? I looked at the current lav sinks at home and it looks like I can go up to 22" or more.

 

[wwhitney]

Just curiosity though, is the main reason that kitchen sink drain should be below lav drain because of the drain fixture unit (dfu); sink = 2 & lav = 1?

No, it's just that as a class lavatories tend to be shallower than kitchen sinks, and kitchen sinks sometimes have garbage disposals. So even if either order works for what you have today, it's a better choice in the long run.

As to the second question, find one of those threads as I suggested.

If you use a 2x2x1-1/2 street san-tee directly into a 2x2x1-1/2 san-tee, then the two 1-1/2" side inlets will be 4-1/16" apart. If you use two regular 2x2x-1-1/2 san-tees with a small piece of pipe and the hubs touching, they should be about 4-5/8" apart. And of course with long pipe segment you can get any separation greater than 4-5/8". (All per Charlotte's catalog).

Cheers, Wayne

 

[Chulapol]

As to the second question, find one of those threads as I suggested.

If you use a 2x2x1-1/2 street san-tee directly into a 2x2x1-1/2 san-tee, then the two 1-1/2" side inlets will be 4-1/16" apart. If you use two regular 2x2x-1-1/2 san-tees with a small piece of pipe and the hubs touching, they should be about 4-5/8" apart. And of course with long pipe segment you can get any separation greater than 4-5/8". (All per Charlotte's catalog).

Yes, I will do some searching about the stub-out height. These are very good information. Thank you very much.

 

[Chulapol]

Also, this is the first time that I learned about "street san-tee." I looked around and don't think i could simply obtain one around here.