DWV design help.

[Mr.K]

As per post #2 "horizontal double wyes should be avoided in favor of individual wyes."

The reason is that with individual wyes you can set the slopes of the branch inlets independently. While a double wye is a "flat" fitting, so at best the two inlets are level with each other, and they have 70.7% of the slope of the barrel. Or worse if one inlet is higher than the other, the lower inlet may have flat or reverse slope.

Cheers, Wayne

Thanks again Wayne!

It’s not that I’m not content at all. I just have one chance at this before I pour and wanted to ensure I wasn’t missing anything.

Things are coming along nicely with construction and should be ready to pour soon.
On question I have is regarding the clean out:
Can I move the clean out to the outside of the back of the foundation? That would mean that the WC would have a pipe running out back behind it and the clean out would pop up outside. Is this allowable?

What do you think about using this small modification? Do you think this would work? I will still be venting as you described.

 

[Mr.K]

I am not a plumber, but I suspect it is very good. Having an outside cleanout would keep the machine outside. Any bends should be 45s or long sweeps.

I think when wet venting the toilet, a lot of people would feel better if your toilet waste joined in horizontally via a wye and maybe a 45, rather than from above. See Figure 1 on page 12 of https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf

Notice how the wet vented stuff comes in from the horizontal.

I see. Thank you for the link! That’s a great resource.
So, more like this? And then behind the WC wall I will add two 45’s to get the clean out just outside the foundation wall.

 

[Sponsor]

 

[Mr.K]

One other question. Is there a required minimum distance between the WC wye drain and the other smaller wye’s for the bathtub and laundry drain? I understand that there must not be hub on hub, but can I make these 3-4” long without any trap siphoning issues?

 

[Jeff H Young]

Any length works between the wyes

 

[Mr.K]

Is this vertical drop from the shower line allowable on the wet vent? Or should the wye be rotated to be more flat? If allowable I will be positioning the other wye in a similar fashion.

 

[Reach4]

Nope, shower is not vented before the trap arm falls. Instead dry vent the trap arm before the fall, and bring that in as the vent for the toilet before the toilet waste joins anything else.

 

[Mr.K]

Nope, shower is not vented before the trap arm falls. Instead dry vent the trap arm before the fall, and bring that in as the vent for the toilet before the toilet waste joins anything else.

In our state we can wet vent the shower and WC through the lav.

I am more curious about the drop after the shower pipe runs 1/4” to drop into the main. It is almost straight down.

 

[Jeff H Young]

why not put a 3x3x2 santee on tope of that 3 inch santee picking up w/c then run vent up.

 

[wwhitney]

In our state we can wet vent the shower and WC through the lav.

Sure, but when wet venting, the connection to the lav drain (the 3x3x2 wye in your picture) is the vent connection. And the trap arm can only drop one pipe diameter at most between trap and vent connection. So to wet vent you either need to lower the trap and roll the wye to horizontal, or combine the shower and lav drain at a higher elevation.

Cheers, Wayne

 

[Mr.K]

Thank you all!

 

[Mr.K]

Is this vertical drop from the shower line allowable on the wet vent? Or should the wye be rotated to be more flat? If allowable I will be positioning the other wye in a similar fashion.

I like this idea…
I have made some adjustments. So, because the utility sink/laundry drain is not part of the wet vent I can drop it into the 3” at a steep angle. The adjustment was made to the shower/tub here to drop it in just above the WC as part of the wet vent system. This is looking better. Thanks Jeff!

 

[Mr.K]

Here is what I have roughed in so far. The drain on the right drops at the steep angle but is also vented per the design. Is there any reason this shouldn’t be good? Thoughts?

 

[Mr.K]

Sure, but when wet venting, the connection to the lav drain (the 3x3x2 wye in your picture) is the vent connection. And the trap arm can only drop one pipe diameter at most between trap and vent connection. So to wet vent you either need to lower the trap and roll the wye to horizontal, or combine the shower and lav drain at a higher elevation.

Cheers, Wayne

The shower and lav drain have been moved into the 3” stack at a higher elevation. Is there reason that this design shouldn’t work?

 

[wwhitney]

Here is what I have roughed in so far. The drain on the right drops at the steep angle but is also vented per the design. Is there any reason this shouldn’t be good? Thoughts?

As long as the following are true, the venting is good:

- The top of the 3x3x2 san-tee is getting a minimum 2" lav drain that is dry-vented above the slab with a 2" vent.
- The laundry drain on the right is also getting dry vented above the slab.
- The elevation drop from the shower p-trap outlet to the 3x3x2 san-tee is less than 2".

Cheers, Wayne

 

[Mr.K]

As long as the following are true, the venting is good:

- The top of the 3x3x2 san-tee is getting a minimum 2" lav drain that is dry-vented above the slab with a 2" vent.
- The laundry drain on the right is also getting dry vented above the slab.
- The elevation drop from the shower p-trap outlet to the 3x3x2 san-tee is less than 2".

Cheers, Wayne

Yes, in that case you'd want a 3" vent through the roof. So you could do something like below. Where the red circle in the wall is the cleanout, and I fixed the lav stub-out to be green (1.5").

The jog between the 3" stack in the wall and the 3" building drain in the slab is not necessary, it's just left over from the previous drawing. So you could route the 3" differently. The important part is the order in which things connect, and using the right fittings.

Cheers, Wayne

View attachment 85772

Thanks again for the quick response. Can you please clarify this. You said 1.5” in one post then recently 2” min on the lav drain. I was planning on having the 3” vent going through the roof with a 1.5” lav drain dumping into it just above the WC.

 

[wwhitney]

Yes, sorry, I didn't review the thread and I forgot that you need a 3" vent through the roof.

My earlier drawing is correct, so 3" vertically up through the roof, with a 3x3x1.5" san-tee for the lav trap arm. So the 3" below the san-tee is the lav drain, and the 3" above the san-tee is the dry vent. The lav trap arm can be up to 42" long if you use a 1.5" lav trap, or 30" if you use a 1-1/4" lav trap.

Cheers, Wayne

 

[John Gayewski]

The shower and lav drain have been moved into the 3” stack at a higher elevation. Is there reason that this design shouldn’t work?

I actually really like this layout. This is one of many advantages of running your main deep (3 to 4 feet) and having branches at shallow elevations. You can do about anything with some depth, and can run piping with really nice layout. While at the same time doing relatively little excavation.

People think they are saving a lot by digging as little as possible, but they then end up with some piping that is less than ideal.

 

[Jeff H Young]

photo in post 32 is pretty typical of what Ive done in my standard ground work of cource we dont hand dig . the only slight concern can be the inspectors like pipes to cross footing either perpendicular or 45 degrees max . perhaps combi up for lav 3 or 4 foot from wall so your not running "in " the footing . BTW I like the cleanout outside in the dirt better than wall clean out like your doing .