Bathroom Reno - Toilet venting question

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Hi,

I am currently adding an en-suite bathroom and have run into a bit of a problem. The existing toilet will now be drained into a 3" branch circuit and I am over the 8 FU's for a 3" wet vent to meet code (double lav w/ 1.5" traps, shower, bath, and w/c - all individually dry-vented elsewhere upstream). What are my options? I know the "trap arm" is effectively over at my new wye so the vent needs to be before it. Is my only option to add a vent from the vertical drop to the back wall (green line in picture)? The only fixture draining into the stack above this is the lav for the existing bathroom, the existing bathtub drains at the same height (left in picture). If the answer is YES I absolutely need that vent, is it something I can get away with for now? (it would involve tearing into the only bathroom that isn't currently in shambles). No inspections required here and that bathroom is next on my renovation list so it wouldn't be too long before I can address it properly.

flat-01-ventQ.jpg


Thanks!
 
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wwhitney

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I am currently adding an en-suite bathroom and have run into a bit of a problem. The existing toilet will now be drained into a 3" branch circuit and I am over the 8 FU's for a 3" wet vent to meet code (double lav w/ 1.5" traps, shower, bath, and w/c - all individually dry-vented elsewhere upstream).
So the WC is the only thing being wet vented?

Regardless, the DFU limit on a wet vent is about the fixtures draining through the wet vent, i.e. the flow in the pipe that is also serving as a vent. As such, the downstream most wet vented fixture isn't included--the part of the system that carries its flow plus the wet vent flow isn't itself a wet vent.

Cheers, Wayne
 

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Correct, that WC is the only thing being wet vented but there will be another WC upstream that is included in the 10 DFU that is dry vented elsewhere. So the pipe serving as the wet vent for the existing WC would be over the limit. I just wondered because it was so close to the stack, maybe it's "ok" without being OK. False hope I guess.
 

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Ah, so my next question, since you say everything upstream is dry vented, is whether you can just run two parallel drains into the 3" line shown in your picture. If you can fit two wyes (possibly street) between the closet elbow and the combo at the bottom of the picture, then you could have a 3" line come in with the WC and a 2" line in with some of the other fixtures. The upstream wye would wet vent the WC.

Also, instead of having wye - wye - combo, you might be able to just have wye-combo or wye-wye by combining the drain currently coming in on the combo with one of the two new drains coming down the joist bay. Depending on the geometry that is cut off by your picture.

Cheers, Wayne
 

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I think I understand what you're saying but sadly I don't think two wye's will fit - it's about 10" from flange to flange my 3" wye's are measuring at about 8". However, maybe I can squeeze in a street 45" at the combo and then a 3" double wye... I might have to go grab one and see.
 

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I just had a thought that I am ending up with the same problem. Functionally, is there a difference between a wye with 10 DFU's up stream and a double wye with 4, 6, and 4 DFU's?
 
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wwhitney

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Double wyes on the flat you have to be careful about, when the barrel is pitched at 2%, and the two branches are at same elevation, they are only pitched 1.4%. So it's better to pitch the barrel at 2.8% to get the branches both at 2%.

That issue aside, if you can replace the combo with a double wye, and then fit a street wye upstream of that on the right branch, the drain coming in the street wye will wet vent the WC, and the other two drains (once of which currently goes to your combo) can go to the double wye.

Or as I elliptically suggested, you could replace the combo with a wye, and put wyes on both inlets. Then from left to right the entries would the drain currently entering the combo; some of your new drains; the new drains that would be wet venting the WC; and the WC.

Cheers, Wayne
 

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So, like this?

flat-02-vent2.jpg


I can probably pull it off, might have to change the toilet flange to an offset one though.

If that's not it then I think you've lost me. If that is, then I drilled a big hole today in the wrong stud bay.
 

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wwhitney

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OK, your new picture renders basically all of my previous comments void. In the first picture I did not notice that stack just partially visible at the bottom of the picture. And I took the 1-1/2" (?) line coming in at the lower left to be hitting a horizontal combo (which is why I kept talking about a combo). Instead you have a san-tee with side inlet.

So in the second picture, what's coming into the side inlet on the san-tee and what's happening above that san-tee (is it a vent only, or is there drainage from above)?

You probably can use a dry vented 2 DFU fixture (which one?) to wet vent the WC upstream of the wye you plan to cut in just upstream of the 3" side entry on the san-tee, but there's some debate about whether the geometry you drew is OK or not. Whether it is allowed will depend on the wording of the horizontal wet venting rules in your Canadian plumbing code, whether the WC drain has to join the wet vent on the horizontal, or if it can join from above as you've drawn. Performance wise, some claim there is a benefit to coming on the horizontal, I'm not sure if that's the case.

Cheers, Wayne
 

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So in the second picture, what's coming into the side inlet on the san-tee and what's happening above that san-tee (is it a vent only, or is there drainage from above)?
1 1/2" drain from the existing bath. Above is a single lav from the existing bath and then nothing but vent.

2 DFU fixture (which one?)
My two new lav's are to that side, so I guess that's 3 DFU, not 2.

Whether it is allowed will depend on the wording of the horizontal wet venting rules in your Canadian plumbing code
I'm not seeing it, but it does ring some bells.

Maybe I am better off with a 45 off the stack and horizontal double wye as that is explicitly mentioned in the code book for installing two toilets: "
where 2 water closets are installed, they are connected at the same level by means of a double sanitary T fitting if the vent pipe is vertical and by means of a double Y fitting if the vent pipe is horizontal" - I'd be down to 6 DFU and the limit would be up to 12 DFU as it would no longer be including the two downstream WC's. I didn't think it would be possible to do it when I first looked at it but now I'm thinking it's my best bet.

I am also rethinking my shower and bath - I can probably just get away with the one vent:


flat-03-shower.jpg


Anyway, I really appreciate the help. I am a bit green when it comes to plumbing - my profession is in heavy construction and residential methods/materials do not come up much.
 
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wwhitney

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Let's see if I have this straight:

The current bathroom has a tub, a lav, and a WC, all connected to that san-tee with side inlet. The lav is currently vertically wet venting WC; is the tub dry vented, or wet vented by the lav as well?

The new bath is going to have 2 lavs, another tub, a shower, and a WC, and your original idea was to dry vent them all (or have the shower wet vent the tub, that looks fine), and the issue is just how to connect the new bathroom drain into the existing plumbing?

So can you not just connect into your stack below the san-tee with side inlet? That avoids disrupting the wet vent on the existing WC. That would cause the new DWV to stick out into the region below in a way you want to avoid? If so, is perhaps raising the san-tee with side inlet up to provide more room below a possibility?

(That would require bringing the 3" WC drain through the double joist, so probably a bad idea. The tub would have to go along if it is wet vented by the lav; if it's separately dry vented, you could just cut a new san-tee in above the existing san-tee with side inlet, using the new san-tee for the raised existing WC drain, and bring the new bathroom drain into the WC's current entry on the san-tee with side inlet.)

Cheers, Wayne
 

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The current bathroom has a tub, a lav, and a WC, all connected to that san-tee with side inlet. The lav is currently vertically wet venting WC; is the tub dry vented, or wet vented by the lav as well?
Correct. The lav is connected above, and the tub is wet vented but could be dry vented (there's a vent literally right there from the bathroom below).

So can you not just connect into your stack below the san-tee with side inlet? That avoids disrupting the wet vent on the existing WC. That would cause the new DWV to stick out into the region below in a way you want to avoid? If so, is perhaps raising the san-tee with side inlet up to provide more room below a possibility?
I did originally consider that. It would require a bulkhead in the ceiling but it's not of major concern as it's above a toilet. No chance raising it up (I actually just added that second joist as there's a heavy tub going in and they carved out the existing for the existing toilet).

I think would rather do some drywall work than cut into the stack and build a bulkhead. So if a 45 and double wye doesn't solve the problem then a dry vent for the toilet it is.
 

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So if a 45 and double wye doesn't solve the problem then a dry vent for the toilet it is.
Not sure if the predicate of that statement was an implicit question or not.

Looks challenging to add a dry vent for that WC if you are also cutting in a horizontal wye between the san-tee with side inlet and the closet bend. A dry vent needs to takeoff vertical (up to 45 degrees off plumb) and stay vertical until 6" above the fixture flood rim. You could cut a 3x3x2 wye (or maybe your code allows 3x3x1.5, the US codes disagree on that question) in upstream of the closet bend, if you can make it to under a wall before coming through the floor while staying at 45 degrees off plumb.

[And actually, in case it would help by lowering the vent takeoff, you could instead replace the closet bend with a wye with the branch inlet pointed up, followed by a 45 to go horizontal. The straight inlet on the wye would be your vent takeoff and would get a reducer bushing.]

Cheers, Wayne
 

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Code allows for 1.5" and I could remain "nominally" vertical to the back wall likely... maybe not. However, it looks like there were only province specific amendments that allow a vent to be added to vertical leg but mine isn't one of them, so I guess that's out of the question? But it also doesn't say I can't...

Say, If I had a vent upstream up of all this mess, would that count as a relief vent? It would be 3" all the way to it and I could make it 2" and completely dry (or wet with either 3 or 6 DFUs).

Maybe not I guess because the vet vented portion would still be over 8 DFUs.

Double wye with street 45 will fit if I change out the existing toilet flange to an offset type (which arguably should have been used in the first place to avoid notching the joist so poorly but I'm guessing they weren't available in the 70's)

Again, I appreciate the help - thanks.
 
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This is sort of what I think I am settled on:


I guess I wouldn't need that dry vent for WC#2 either now would I? They can both wet vent through the Lav drains which I have to run anyway. That would make two large useless holes I have drilled in the bottom plate... oh well.
 

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Code allows for 1.5" and I could remain "nominally" vertical to the back wall likely... maybe not. However, it looks like there were only province specific amendments that allow a vent to be added to vertical leg but mine isn't one of them, so I guess that's out of the question? But it also doesn't say I can't...
Having a dry vent for a WC taken off the vertical fixture drain instead of the horizontal should be allowed and should be non-controversial. For most fixtures with external traps, the vent take off needs to be on the horizontal trap arm before it falls one pipe diameter to prevent siphoning of the trap (the trap weir rule). But that doesn't apply to a WC, as it intentionally siphons its integral trap and then refills it (e.g. the little tube in the tank that sends some of the refill water into the overflow). So unless you see some specific wording prohibiting it (which would make no sense to me), I'd say it's allowed.

Your last drawing looks OK to me, although obviously I haven't read your location's wet venting rules. Since the WC wet vent doesn't extend upstream of the straight inlet on the 3x3x2 wye, you don't need any 3" upstream of that point, so you could use a 3x2x2 wye (i.e. 3x3x2 wye with 2" bushing).

Cheers, Wayne
 
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