WET VENTING A TOILET TO A SHOWER AND TWO SINK CABINET

[Tj1dish]

This forum is really helpful with awesome ideas and Code implications!!

I'm embarking on my bathroom remodeling and before anything wanted to figure out the draining configuration to the existing drain.

It's basement bathroom, is 6' wide only, all is on the same wall and that's why my goal is to use same vent for a two-sink group, a shower and a toilet, and at the same time to go cover for both UPC and IPC.

In the first configuration I use 3" to 2" rolled to 45 wye (if not mistaken Code says not more than 45 deg. for wet vent) to 2" wet vent, above connected shower trap arm that'll be not more than 3', followed up by two-sink cabinet combo (will dry-vent it), clean-out on top before the roof run.

The second configuration is the same, except I replace the 2" with 3" the wet section, this would be kinda tight though.

I attached here some pictures, please give me your advice and blessing does it look good /which one to go with?

 

[Reach4]

(if not mistaken Code says not more than 45 deg. for wet vent)

I don't know what that would mean.

In Texas, there are different codes in different places, tho most is IPC. Are you in Houston, Austin, or San Antonio?

Are you putting the shower trap arm in a different plane than the toilet for meeting your physical situation?

That said, I suspect your #1 is mostly OK for the codes, but that bottom santee would be a combo or wye. See https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf including page 12.

In your title you mention "two sink cabinet", but your mockups don't seem to address that. Two lavatories in the same bathroom?

 

[Sponsor]

 

[wwhitney]

Are you putting the shower trap arm in a different plane than the toilet for meeting your physical situation?

I expect he's doing that to comply with the UPC requirement that the WC be the last fixture on the wet vent.

So go with a variation on #1: after the closet bend, use a 3x2 combo as Reach4 suggested, rolled 45 off plumb, stay at that angle on the inlet until you go plumb with a single 45, then the san-tee for the shower, etc.

Cheers, Wayne

 

[Tj1dish]

Reach4 and Wayne, thank you for your fast response!


My bad, I attached wrong pic #1 - NO SANTEE on the bottom, I changed it to a 3" to 2" wye.

Reach4, I'm in Houston, just, I always try to meet most restrictive code Also,"(if not mistaken Code says not more than 45 deg. for wet vent)" meant that wet vent entered the 3" drain at 45 degree angle of the horizontal plane(or little less if I can fit it).

Then a single 45 to get vertical, then a santee for the shower trap arm, then about 22" above floor level the santee for two lavatories in the same bathroom , then a clean-out and last up is the roof run.

I'll dry-vent the two lavatories additionally back to same 2" vent about 42" above floor.

Horizontally, my shower trap arm is going in a different plane, looks like it will be close to a foot above the toilet drain plane.

Wayne, yes - I'm trying to comply with the UPC requirement that the WC be the last fixture on the wet vent.

I did a 3" wet vent section also with the presumption to keep increasing the size of next drain, only - if I use that 3" to 3" wye to the soil pipe it might mechanically allow for a blockage at the wye. Is that correct?

Please let me know if the 2" wet vent I described above is OK, and preferred against the 3" wet vent option?

Thanks in advance!

 

[Reach4]

I'm in Houston, just, I always try to meet most restrictive code

Houston uses UPC, which is often the most restrictive, but not always.

 

[wwhitney]

For the UPC, you need to carefully parse section 908, particularly 908.1.1:

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/9/vents#908.0

When I first read 908.1.1, I took it to mean the vertical wet vent section has to be one size bigger than the minimum vent size. Since a WC has a minimum vent size of 2", that would mean the vertical wet vent portion has to be 3", i.e. from the sink san-tee downward.

However, it actually says "one pipe size exceeding the required minimum pipe size for the sum of the fixture units served by such wet-vented section," so I take that to mean you just look at the number of fixture units without regard to one of them being a WC. A shower is 2 DFU, a WC is 3 DFU, and a 1-1/2" vent is good for 8 DFU, so 1-1/2" would be the minimum pipe size for the sum of the fixture units. That means the upper vertical wet vent can be 2", from the sink san-tee to the shower san-tee.

The lower vertical wet vent, from the shower to where the drain turns horizontal, needs to be 3", though. 908.1.1 also says the size has to be "one pipe size exceeding the required minimum waste pipe size of the upper fixture". The required minimum waste pipe size of the shower is 2", so the lower vertical wet vent has to be bigger than that.

If you managed to connect the shower trap arm to the lav drain on the horizontal, instead of the vertical, and then bring that to the WC horizontally, you'd only need 2" from the shower to the WC, per 908.2. But that geometry seem difficult or impossible.

Cheers, Wayne

 

[Tj1dish]

Wayne,

I read that 908.1.1 very same way you took it except I thought the wet vent above the shower trap arm to the lavatory arm serves the shower so it has to be 3".
One problem is the space to fit the whole set in.
My other problem is anywhere I look it shows similar setups with a 2" wet vent, that's why I posted two different options.

I'll rearrange it tonight and post a new picture to see what y'all would advise?

Thanks

 

[Reach4]

How about an overhead rough sketch showing the location of the toilet, the shower, the lavatories, soil pipe exit, and also some indication on restrictions on pipe routing, such as joists if pipes are higher than the bottom of the joists.

 

[Tj1dish]

By the way, I'm using a 2" size for my lavatories drain also, that's why I posted pic #2 and #3 with a 3" wet vent all the way.

Any thoughts?

 

[Tj1dish]

Reach4,

I just uploaded a 3D sketch of the bathroom design.

The blue cylinder in bottom right of the image indicates where the soil pipe exit is, the green vertical one is the vent location, in orange is the locations for the shower and toilet drains should be. Lavatories will be dry-vented to the green one.
Hopefully that gives better idea...

 

[wwhitney]

A conventional horizontal wet vent layout would be to have the combined lavs drain enter the slab closer to the vanity. Then it can swing out to farther than 12" from the vent wall to avoid the WC drain and reach the shower trap arm first. Then the WC drain can come in; the horizontal WC fixture drain is limited to 6' by the UPC, but it looks like you could make that work. Everything is 2", except downstream of the closet flange and the individual lav trap arms.

Cheers, Wayne

 

[Reach4]

Red is double fixture fitting in the wall, receiving two trap arms. Only vent into top of double fixture fitting.
Then orange down below floor. Then blue across to big toilet blue.

Shower trap in darker blue joins lavatory drainage, which wet-vents shower and then toilet.

Check distances, which may be limited.

 

[Tj1dish]

My lavatory cabinet is 72" so the length of the wet horizontal vent becomes about 8'...

 

[wwhitney]

Length of the horizontal wet vent itself doesn't matter. What matters is the length of each fixture's trap arm, from the trap to where the vent comes in. Whether that vent is wet or dry.

Cheers, Wayne

 

[Tj1dish]

 

[Tj1dish]

Gents,

This last picture shows what I did, following your advice.
I'm connecting the wet vent from lavatories then shower to the main 3" drain by a rolled up to 45° 3x3x2 wye.

Hopefully the rest is ok but I have two questions:

1. Is it ok to roll up on 45° the 3x3x2?

2. Is it ok to use 2" for the lavatories trap arm as the wet vent below is 2" too?

Thanks in advance!

 

[wwhitney]

0) I take it the open 3" elbow is the closet bend for the WC? If so, is the distance from the top of the closet flange to the 3x2 wye wet venting the WC going to be under 6'? That's a UPC requirement. (IPC has no limit)

1) I think you may find some difference of opinion on that. I'm of the opinion that if it's under 45 degrees rolled up, it's still horizontal, so it's fine for horizontal wet venting, having seen no performance or code evidence to the contrary. I've seen it said that horizontal wet venting should be as close to true horizontal as possible, so more like 1/4" to 1" per foot slope.

You could get closer to the latter by angling the 45 outlet downward more, so that you fall a little faster in the next segment (and I think be a little closer to parallel to the 3" line in plan), and can roll the wye down closer to horizontal, also dropping the p-trap a little.

You could also move the double fixture fitting towards the camera, so that your lavs drains doesn't have to cross over the WC, allowing you to lower the lavs drain vertical to horizontal transition, and/or use a LT90 or 45 + 22.5 instead of the 45 to avoid the cross over.

2) Yes, that's fine, although somewhat non-standard and more trouble to route through walls, but required by the UPC if your trap arm (including the part outside the wall) is over 42". (Obviously moving the double fixture fitting may increase one trap arm length). Where the trap arm is under 42", you could just use a 2" x 1-1/2" bushing in the double fixture fitting side inlet and run a 1-1/2" trap arm, if you like.

Cheers, Wayne

 

[Tj1dish]

Wayne, thank you for your response!

0) The 3" elbow is the closet bend and distance to the 3x3x2 wye is about 4'.

1) Your note on that makes sense, I didn't see it.

2) I can do the trap arm 1-1/2" , I'm just always overkilling

 

[Tj1dish]

 

[Tj1dish]

Please take a look at the last picture I took,

I'm always trying to simplify and so far this kind of set up seems the simplest so I wanted to see what y'all would say?

First, since my drain to outside is 4" this time I'm using a 4" for the toilet.
Before the elbow for the closet bend I have a wet vent started with a 4x4x3 wye, then a 3" long sweep, then a 3" pipe (not on the picture), then a 3x3x2 santee for the shower trap arm which will be less than 4' in length, then a 3x2 flush bushing, than a 2" pipe, than a 3x3x2 ( or 3x3x1-1/2 eventually) santee for the lavatory trap arm, which will be less than 4' in length but I'll still dry-vent it, and that's where the end of the wet vent.
Of course will have a clean-out above it and then continue in 2" to the roof run.

I know that showers take lots of hair and soap and that mixture brings a nasty build up inside the pipes - in my other bathroom I used a drain with a hair strainer and this thing fills up fast!

Also, I have concerns about lavatories, toilet and shower to be syphoning each other...

Maybe I'm missing something or the horizontal wet venting has to be preferred but I hope last set up is by the UPC and y'all approve it - it just gives me a piece of mind that shower wouldn't fill up with gray water from an eventual back up, just thinking about it gives me the chills

Please let me know what you think?