Sub Slab Advice

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wwhitney

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Ok, an idea is below, maybe others will have a better idea. A few preliminary comments:

- UPC requires a 2" vent for a WC, and that includes a vent and drain for a lav that is wet venting a WC. Probably this came up already, but your green circles don't indicate the vent size.

- I was thinking that routing the building drain under the bottom bathroom WC is not as good as routing it to one side. But I'm perhaps mistaken, since the building drain is going to be a lot lower. That means you can just do your horizontal drainage and wet venting for the bathroom at a higher elevation, and then if the branch drain ends up directly above the building drain, just 45 down to an upright wye in the building drain.

- So I drew the idea below with the building drain to one side (and at an unspecified location), but you could do the same thing with the building drain under the lower (on the page) WC, if that works out better for where you emerge to connect to the building sewer.

- The basic layout is predicated on the idea of wet venting the shower via the half bath lav, rather than the full bath lav. The laundry sink and standpipe get dry vents, of course. I show the laundry sink/standpipe drain hitting the bathroom group but it could instead connect separately to the building drain.

Cheers, Wayne

Capture.JPG
 

Jayjayla

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Ok, an idea is below, maybe others will have a better idea. A few preliminary comments:

- UPC requires a 2" vent for a WC, and that includes a vent and drain for a lav that is wet venting a WC. Probably this came up already, but your green circles don't indicate the vent size.

- I was thinking that routing the building drain under the bottom bathroom WC is not as good as routing it to one side. But I'm perhaps mistaken, since the building drain is going to be a lot lower. That means you can just do your horizontal drainage and wet venting for the bathroom at a higher elevation, and then if the branch drain ends up directly above the building drain, just 45 down to an upright wye in the building drain.

- So I drew the idea below with the building drain to one side (and at an unspecified location), but you could do the same thing with the building drain under the lower (on the page) WC, if that works out better for where you emerge to connect to the building sewer.

- The basic layout is predicated on the idea of wet venting the shower via the half bath lav, rather than the full bath lav. The laundry sink and standpipe get dry vents, of course. I show the laundry sink/standpipe drain hitting the bathroom group but it could instead connect separately to the building drain.

Cheers, Wayne

View attachment 82099
Ok, so you can wet vent a shower with a sink and toilet in a totally different room, I didn't know that.

So you're saying the main building drain is directly under the wall between the two toilets. I just thought it would be easy to combo straight down from the toilet and also pop straight up to the washer. The main will be over 20" deep by the time it gets to this point. I honestly won't know what is easier until I'm out there playing with fittings so I'm open to any opinions. This seems better in a lot of ways because there seems to be more room to tie in.

It does get a little tight in there how I was drawing it. Is there a code on how close fittings can be when you tie into the main? So if I combo or wye in, how far downstream can I combo in next?

You're correct on the green dots, they were just a pain to get rid of on my software. The only 1 1/2" vent in the entire house is the kitchen island.

Thanks Wayne
 

Jayjayla

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If I did go directly under the second toilet, I would have to tie in the lav either on the vertical up to the WC with a 3x2 combo or on the main drain. Would the WC be considered vented if the lav is not tied directly into the toilet branch or would the toilet have to have its own vent? In other words, can you wet vent directly off the main drain? Just feels kinda tight in there both your way and the way I was thinking. Mine might not be up to code though depending on where you can tie the lav in.
 
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wwhitney

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A horizontal wet vent can only carry drainage from bathroom fixtures, and only from one bathroom (edit: bathroom group) (UPC). So as the building drain will be carrying the kitchen, etc, if the path from the WC to the lav's vent passes through the building drain, it's not a wet vent.

With the main 20" deep by the time you reach the bottom (on the page) bathroom, I don't see the issue. Under the WC you can have a closet bend (quarter bend) pointing towards the bottom of the page, the lav can wye in on the horizontal, then you hit a 45 and then an upright wye on the building drain.

I think 20" of height should be enough for that. If the main is 4", then a 4x4x3 wye upright with a 3" street 45 has a diagonal run of 9-1/4", or a height gave between the horizontal 4" and the 3" of .707 * 9.25 = 6.54". If you don't want the horizontal 3" line to 13.5" deep, you can use a regular 45 into the wye.

Cheers, Wayne
 
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Jayjayla

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That's a great description of wet venting code, thanks.

You're talking about the upper bath where we're now connecting the shower to? That one seems easy, lots of room. Its the toilet/lav below the laundry room that feels tight.

I was thinking something a little similar to how you drew the half bath originally. Extend the 3" past the lower WC through an upright combo under WC and reduce to 2" up to the lav/vent. Then tile the laundry room into where you suggested on the other side.

I won't know until I start playing with it off of a damb computer but it feels like in that 16" space I'll only be able to fit so many fittings in there especially on the 3" pipe.
 

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wwhitney

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You're talking about the upper bath where we're now connecting the shower to? That one seems easy, lots of room. Its the toilet/lav below the laundry room that feels tight.
No, I was talking about the WC/lav below the laundry room. And how to connect just those on a branch of the building drain, if it runs under the WC location. The laundry standpipe/sink and the WC/lav/shower would each be separate branches of the building drain.

Below is a rough isometric of my textual description.

Cheers, Wayne

Isometric.jpg
 

Jayjayla

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No, I was talking about the WC/lav below the laundry room. And how to connect just those on a branch of the building drain, if it runs under the WC location. The laundry standpipe/sink and the WC/lav/shower would each be separate branches of the building drain.

Below is a rough isometric of my textual description.

Cheers, Wayne

View attachment 82140
Ok that makes sense thanks. I guess either way you drew it will work which is nice to know. I'll just bring extra fittings. Side note, is it not allowed to do an upright combo in the main drain? Does it have to be a wye? It would make sense being a wye, I suppose less of a splat, which is why I ask.

So would the way I drew it be ok too?
 

Reach4

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A combo is the combination of a wye and a 45. I expect a combo is fine wherever a wye is fine unless the extra 45 degrees of bend crosses some threshold. But if your setup is similar to that last sketch, how would a combo make things easier for you?
 

Jayjayla

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A combo is the combination of a wye and a 45. I expect a combo is fine wherever a wye is fine unless the extra 45 degrees of bend crosses some threshold. But if your setup is similar to that last sketch, how would a combo make things easier for you?
It wouldn't, I'm just talking in general. It would be a combo pick up the WC and keep going then reduce to 2" to pick up the lav.
 

wwhitney

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Sure, you could use a combo, but why use 2 90s (combo plus quarter bend) when you have the available run for 2 45s (wye plus 45)? I don't see space as being tight in that dimension downstream of that WC.

Cheers, Wayne
 

Jayjayla

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Sure, you could use a combo, but why use 2 90s (combo plus quarter bend) when you have the available run for 2 45s (wye plus 45)? I don't see space as being tight in that dimension downstream of that WC.

Cheers, Wayne
Agreed, thanks
 
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