View Full Version : Adding a Bathroom to a bungalow attic - Toilet Venting Question

06-06-2011, 07:46 AM
1321813217I am adding a large bathroom in an attic with double lavs, a shower and toilet. Based on my floorplan, I am venting everything individually because I do not want to drill through the floor joists. Since my lavs and shower will have a plumbing wall, I am going straight through the roof for venting, which is intuitive and easy. However, my toilet is on the other side of the room and I would like to tap into to my original 4" dry vent for my first floor fixtures, in order to vent the toilet. I have attached the picture. I need to get the low-heel 1-1/2" connection tapped into my 4" vent. Are there any restrictions or general rules that dictate how I do this? For instance, can I only tap into the 4" at a certain height? Or can I only have a limited number of turns? Ideally, I would like to run the 1-1/2" in the sub-floor (with a slight upward slope) around the 4" drain and then connect on the backside (rightside in the photo). I want to build a short wall for astetics on the left side of the 4" dry vent. Also, can I use a 3" street 90 degree bend as my toilet connection? Or do I have to use a 4" to 3" closet bend? (In the picture I have a 3" street 90.

06-06-2011, 08:03 AM

06-06-2011, 09:07 AM
13219Okay, I will check into the 2" VS. 1-1/2" toilet drain. If I need to use a 2", is there a similar option for the 3" pipe using a low-heel connection like I have already purchased, assuming I was going to use 1-1/2". Other than not accurately drawing the reverse pitch, are the markings on my picture an accurate visual description of what I can do?

06-06-2011, 09:47 AM
You would be better off venting the toilet lower using a 3x2 wye fitting. That way you can continue up with the vent with less bends.

The lav needs a 2" where the two combine. Also you will need to either vent each one, or use something like a fixture cross you are only venting once.

The fitting for the 4" needs to be a shielded coupling, not a rubber fernco. A rubber fernco can only be used in the dirt (below grade).

Plumber2011, I'm glad you added the tool belt; it was a bit risqué before.

06-06-2011, 10:50 AM

06-06-2011, 11:42 AM
So is my venting sufficient for the double lavs? Everything is run in 2" in that pluming wall.

Here are a few changes I will make and other thoughts:

1) Change to a 4" shielded coupling on the dry vent
2) Replace the 2"elbow currently facing upwards with a 90 degree 2" street elbow turning horizontal, then reduce down to 1-1/2"
3) I checked with a local plumber, and he said I could use 1-1/2" vent for the toilet, since it was only venting that fixture and it is a dry vent.
4) Can I put my 2" vent Tee under the 2" tee catching the lav? (As pictured it is above and I think it may be too high at 26"). Is there a rule of thumb for the height that the drain should come out of the wall?

06-06-2011, 12:55 PM

06-06-2011, 02:17 PM
Can I keep my existing tee on the right side where it is now, or do I need to move my drain opening to the left, so it not at the vent tee? From Terry's message, it almost seemed like I needed to relocate that drain, so the vent would count for both sinks. Is that accurate? If I can keep the height of the holes I have already bored out, and keep the location of the drain/vent tee on the right side, can I move the drain tee beneath the other tee so my drain would be lower? Also, will is there any code around the height of the drains? I would prefer not to have to rip those studs out and replace if I do not have to (assuming my vanity height/sink depth will be compatible their existing locations. Let me know. Thanks for the help guys!

06-06-2011, 04:00 PM
Can't tell from the discussion......you aren't planning to send your attic toilet waste down the vent from the first floor are you?

06-06-2011, 04:04 PM
Because your lav basins are draining into the vertical pipe at different elevations, (as in the original picture) it is considered a wet vent. To meet WI code for a vertical wet vent, the drain between the two fixtures must increase one pipe size AND be not less than 2".

If your right tee is 2x2x1.5, you are good, as long as you turn the bend on the right basin so it is coming straight out of the wall (without the vertical drop).

Edit -- I have the same question as Jim about how & where your drain connections are being made.

06-06-2011, 04:52 PM
No, I am adding a secondary 3" stack, which I will tie into the main stack, beneath where the 1st floor lav, tub and toilet tie in.

06-06-2011, 04:56 PM
Yes, it is a 2" x 2" x 2" (even have a 2" vent for this one, just to keep it simple). Also, I think you meant I need to turn the bend on the left side, correct? Can I swap the locations of the two tees on the rightside, in an effort to get the drain coming out of the wall lower, as I think I am too high right now (26"). I dont want to stud the wall if I do not have to...

06-06-2011, 05:14 PM
The top tee must be a 1.5" arm dumping into the 2" vertical drain.

The tee 14-18" off the floor will work for a common vanity. 26" will be too high for the trap.

I would cut the studs out and install new ones.
I see plumbers doing it, but 60% is the max hole permitted in a non-bearing wall per the IBC.

06-07-2011, 05:50 AM
I think you should have decided on the lavatory drain configuration BEFORE you drilled the holes. WE do not have measurements but it appears that BOTH sink drains may be too high. I would have done the entire system differently.

quote; I see plumbers doing it, but 60% is the max hole permitted in a non-bearing wall

Well that would pretty much exclude a lot of horizontal in wall piping.

06-07-2011, 07:09 AM
agreed, I started re-doing it last night...it is a good thing PVC/wood studs are cheap! One of my friends is helping me with this and I just think he was moving too quickly. I will post the new (and improved) picture tomorrow or Thursday.

Nothing like doing things twice..."If you dont have time do it right, when you have time to do it over again?"

Tom Sawyer
06-07-2011, 01:08 PM
IPC allows 1 1/2 to be used as the wet vent leg for a bath group now.

06-07-2011, 02:56 PM
IPC allows 1 1/2 to be used as the wet vent leg for a bath group now.

Maybe true, but WI has it's own plumbing code.

06-08-2011, 05:15 AM
Is this better? I made the following changes:
- changed the piping for the lavs to 1-1/2" (on the slope, still 2" going down to the basement"13243
- re-studded the walls and put smaller holes in the studs
- lowered the holes

06-08-2011, 05:48 AM
I, and most inspectors, would NOT approve that right hand sink being connected that way. It was CORRECT the way you originally had it. The problem was with the left hand one.

06-08-2011, 06:31 AM
Really? Why not? This was actually the way it was suggested to me by a licensed plumber. Another more general question, I need to cut-out a piece of the cast iron and replace with a 4" x 3" wye and a 4" cleanout. Is there any issue with using PVC for this (per code). I hear a lot of people recommending that the CI is used to replace the CI cut-out, but there is a lack availability in this area so I would like to use PVC if I can.

06-08-2011, 10:41 AM
No plumber would recommend plumbing the two lavs that way.
We have gone over this many times on this site.

Cast iron fittings are availible at a plumbing supply, not a big box store.
I find it always easier to cut in cast iron with no-hub coupings then it is to use plastic fittings, which by the way are a different size on the OD.
Measure your cast, and if it's 4-1/8" OD, then you will need a cast iron x copper no-hub coupling. New cast iron fittings are 4-3/8".
And PVC is a little bigger then that.

06-08-2011, 11:12 AM
That is interesting, because for some reason, this is what he told me what to do, with an isometric picture. Is this technically against code? If not, what is probably why he told me to do it this way. The way I look at it, as long as the water flows down the drain, I will be fine :) I will check out the plumbers supply for the CI fittings. Although, I did rip out about 300 lbs of copper on the 2nd floor/attic, so I am less concerned about using PVC than I originally would have been.

06-08-2011, 11:42 AM
300 pounds of copper should fetch you quite a bit of money at recycle.

06-08-2011, 11:52 AM
too late, someone grabbed it out of my lawn while I was cutting it out. These scrappers are quick!

06-08-2011, 12:11 PM
Damn @ $ 3.00 per pound that would have payed for your restore.

Tom Sawyer
06-08-2011, 12:38 PM
I don't necessarily like it piped like that but, they are both part of the trap arm and both IPC and UPC will allow them in that configuration.

06-08-2011, 12:45 PM
1324713246but back to plumbing....Can someone help me understand why the way I set-up the lavs is not a good idea? Even if it is a link to this same type of conversation in the past. Check out the isometric the licensed plumber drew for me. Is that incorrect?

06-08-2011, 12:47 PM
Okay, that is what I am looking for. I understand the plumber I spoke with may not be as focused on quality as the pros on this forum. You guys seem to be very dialed-in and certainly know your craft, I am just trying to learn. Why do you guys not like this configuration? I would like to know so I too can pass on this wisdom someday when another plumber tells me this is the "right" way to do it.

Tom Sawyer
06-08-2011, 02:11 PM
It can be difficult to clean if it plugs up. some will argue that the san tee on it's side is a problem but it is washed by both fixtures and withing the trap arm so it passes. Any inspector that is using the IPC or UPC and does not pass it needs to bone up on his code.

06-08-2011, 02:56 PM
Thank you Tom. I appreciate the unbiased response, understanding that this may not be the "ideal" set-up for the pro plumber. I am actually excited for what the inspector will say about this.

06-08-2011, 04:45 PM
I don't think I would be excited.
You have created a horizontal wet vent in the last few inches of the arm. The sani-tee on it's side is not specifically prohibited, but a horizontal wet vent has to be 2" pipe. I suppose you could re-vent the left side.

I hate to say it, but IMO, what you have now is not any better than what you started with.

The inspector will have the final say & some are pickier than others.

Don't forget to put in nailing plates and test tees for your stack test.

Tom Sawyer
06-08-2011, 05:42 PM
How is the last few inches of the trap a horizontal wet vent? It's not a vent at all. the vent starts where the trap arm enters the vertical san tee.

06-09-2011, 06:26 AM
From a common sense standpoint, the lav on the right should flow exactly like the lave on the left. Also, since the trap serves a clean out, this will be very easy to clean, if for some reason, it gets clogged. Back to the toilet, I went with the 3" street 90 turn for my toilet connection. I only did this because I really need to be careful how far the toilet sticks out. Can someone confirm for me that this is legal? I was going to use the 4" to 3" 90 degree turn, but it would've moved my toilet atleast 3" farther into my floor plan. The rational I used is that the toilet has a 2" trap built-in, so if the waste gets down that smaller trap, it should certainly get through a 3" 90 degree bend. Please confirm I am correct here.

06-09-2011, 07:20 AM
What they are saying is that if enough flow from the left lav went through the pipe, you could pull water out of the trap on the right lav. A re-vent between the two lavs should prevent this.

06-09-2011, 09:15 AM
Got it, that makes sense...I will add if the inspector sees fit. Any input on my street 90 bend for the toilet? Am I good there?

Tom Sawyer
06-09-2011, 08:07 PM
What they are saying is that if enough flow from the left lav went through the pipe, you could pull water out of the trap on the right lav. A re-vent between the two lavs should prevent this.

Never gonna happen with a modern lav with a pop up drain.

06-10-2011, 05:09 AM
Maybe not, but that is the thought as to why it may not pass. Also, the inspector does not know what kind of lav that you are putting in during this stage, so he may want to see a revent.

06-10-2011, 06:12 AM
I will let you guys know what he says.

Can someone please tell me if I can use a 3" street 90 beneath my toilet flange. I have had two plumbers tell me that I can but apparently the plumbing code is up to a lot interpretation. I know that when you go from a vertical run to horizontal that you are suppose to use long turns, which is why I am having a tough time understanding why I can use a street 90 for the toilet, considering the run is going from vertical to horizontal. I am assuming toilets are somehow different.

Let me know about that one. I appreciate the help so far, I am learning.

06-10-2011, 06:25 AM
A closet bend is an exception to the rules requiring drainage ( meaning sweep) fittings. Maybe so of the real oldsters ( I am only 66!) can explain how that came about. It may have been a practical acceptance of the need to install toilets in 2x8 joist ceilings?

06-10-2011, 06:30 AM
2" x 8" is what I am working between. So a 3" street closet bend is just as legal as 4" x 3" closet bend?

06-10-2011, 12:30 PM
Here is what my stack looks like so far...I did go with the 2" low-heel connection, just to be safe. My major focus is on around this 3" street 90 closet bend.13254

Tom Sawyer
06-10-2011, 01:20 PM
What you have there in the picture is good.

06-12-2011, 06:12 AM
My old cast iron 4" main stack does not have a clean plug, but I am going to add one in my remodel. Does my new secondary 3" stack going up to the attic also have to include a cleanout plug? Or does the cleanout on main stack serve as the cleanout for that stack as well? Lastly, where do these test tees go? Are they mandatory?

EDIT: I have had (2) plumbers tell me that toilet is actually a cleanout on a vertical run, which makes sense, because if the toilet is removed, I could easily snake this 3" secondary stack. Understanding again, that this may not be the ideal location. However, I am tight for space in the basement and do no want to add another 3" tee or wye in my secondary stack if I do not have to.

Tom Sawyer
06-12-2011, 06:47 AM
where impractical to install a vent the toilet may be used as a clean out.

06-13-2011, 06:10 AM
13275Wow, big weekend....I tapped in the main stack yesterday. Good news, NO LEAKS! Please take a look at the photo. I am thinking I need to add a test at the end of the 2" run that goes back towards the other side of the basement. At that point, the pipe turns at 90 degrees and goes another 6' between the floor joist before it goes straight up to the bathroom. From the code book I read yesterday, it seems that I need a test tee whenever there is a horizontal change in direction of 45 degrees or more. Can someone confirm that. Also, where the vertical pipe enters the basement for my separate lav/shower 2" drains, are long 90s okay there, or do those also HAVE to be test tees?

EDIT: Sorry Terry, even the largest plumbing supply house did not have the cast iron wye I needed for this project. They guys told me that no plumbers in this area are using cast iron for home replacements anymore, so they do not carry it.