Lavatory absolutely need a dry vent above?

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Cheers, Wayne
The new and (hopefully) improved plan. I forgot to note the circle at the tub is the usual drain/overflow kit.

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Reach4

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1. On top bathroom, join the lavatory drain farther upstream so that you don't have two things upstream of the lav drain.
2. On top bathroom, I presume darker line is lav drainage. That drain path does not make sense to me. Can you join the lav drainage with the shower drain before you hit the toilet? That could be via the lav drain going over the 3 inch, or the 3 inch being moved lower in the drawing.
3. Not important, but I would think the lower lav drain would pass under the floor toward the red, and could cross at an angle, rather than following walls.

I may well be missing something.
 
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1. On top bathroom, join the lavatory drain farther upstream so that you don't have two things upstream of the lav drain.
2. On top bathroom, I presume darker line is lav drainage. That drain path does not make sense to me. Can you join the lav drainage with the shower drain before you hit the toilet? That could be via the lav drain going over the 3 inch, or the 3 inch being moved lower in the drawing.
3. Not important, but I would think the lower lav drain would pass under the floor toward the red, and could cross at an angle, rather than following walls.

I may well be missing something.
Point 1. absolutely...I will adjust, I have two connections before the vent...not good.
Point 2. I can see what you are saying, Wayne had indicated either way would be fine. Can you describe why it does not make sense to you?
Point 3. What would the angle gain me?

I also have drawn this with complete disregard to the 6 or 7 piers in this area...things may well change...but it is a good starting point?
 

wwhitney

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1) Yes, the lav drain is the vent for the WC and the shower, so the lav drain needs to hit the individual WC or the individual shower first. Then the combined lav/fixture drain can hit the other individual fixture drain.

2) I don't follow Reach4's comment, I don't see the issue (besides 1). But Reach4 makes a good point that if desired you can have the lav/shower above the WC.

3) Also not following. The light green is the above floor trap arm, the dark green is the below floor drain. Looks fine to me.

Cheers, Wayne
 
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1) Yes, the lav drain is the vent for the WC and the shower, so the lav drain needs to hit the individual WC or the individual shower first. Then the combined lav/fixture drain can hit the other individual fixture drain.

2) I don't follow Reach4's comment, I don't see the issue (besides 1). But Reach4 makes a good point that if desired you can have the lav/shower above the WC.

3) Also not following. The light green is the above floor trap arm, the dark green is the below floor drain. Looks fine to me.

Cheers, Wayne
I think his number 2 was meant to say lower bathroom...at least that was the only way I could make sense of it. Then he would be saying to tie in to the shower like you had drawn.
 

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It was not clear to me what the upper darker green line represents. It may be that there is a santee under the dot labeled "vent to top of cabinet level. In that case, the trap arm is turning the corner in the wall to get to that santee. But in that case, the light green line, which I presume is a vent doesn't make sense to me.

What am I misreading?

And that is OK. santee centered behind the lavatory seems better to me.
 

Reach4

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It was not clear to me what the upper darker green line represents. It may be that there is a santee under the dot labeled "vent to top of cabinet level. Then a drain line represented by the darker green would make sense in that case. Also in that case, the trap arm is turning the corner in the wall to get to that santee. But the santee to the left does not seem to call for the light green line, which I presume is a vent.
What am I misreading?

Santee centered OK... maybe 2 inches off-center behind the lavatory seems better to me.
 

wwhitney

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Light green = trap arm above the floor. Dark green = lav drain below the floor. At the transition is a san-tee. Dashed blue is dry vent above the lav flood rims.

On the lower lav, the wall behind is brick and can't take any drains or vents. So the trap arm goes to the right side to reach a framed out area. On the upper lav, the only reason the trap arm goes to right behind the lav is to get to a more convenient location to enter the floor system, given the need for the lav drain to hit the WC or the shower first, before those two drains combine.

Cheers, Wayne
 

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Got it. I thought light green was vent, rather than trap arm.
 
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Light green = trap arm above the floor. Dark green = lav drain below the floor. At the transition is a san-tee. Dashed blue is dry vent above the lav flood rims.

On the lower lav, the wall behind is brick and can't take any drains or vents. So the trap arm goes to the right side to reach a framed out area. On the upper lav, the only reason the trap arm goes to right behind the lav is to get to a more convenient location to enter the floor system, given the need for the lav drain to hit the WC or the shower first, before those two drains combine.

Cheers, Wayne
Exactly...thanks for clearing it up.
Got it. I thought light green was vent, rather than trap arm.
Reach4, There is a legend at the top of the image you may have missed.
 

wwhitney

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Yes. I missed the legend.
Increase dark green and the pipe below the santees to 2 inch.
Possibly a good idea, and would be required for the UPC (along with a 2" vent), but the IPC does allows a 1-1/2" wet vent to carry 1 DFU, i.e. a single lav.

Cheers, Wayne
 

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Possibly a good idea, and would be required for the UPC (along with a 2" vent), but the IPC does allows a 1-1/2" wet vent to carry 1 DFU, i.e. a single lav.

Cheers, Wayne
Even to wet-vent a toilet?
 

wwhitney

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Even to wet-vent a toilet?
Yes, the IPC only requires a 1-1/2" dry vent for a WC on a 3" drain, and a 1-1/2" wet vent can carry 1 DFU. Add a second lav, or a shower or tub, before the WC, and the minimum wet vent size goes up to 2" at the point where the extra fixtures come in.

I'm a bit unclear whether voluntarily choosing to use a 4" drain for a WC ups the minimum vent size to 2". I.e. whether the minimum IPC vent size is 1/2 of the actual drain used, or just 1/2 of the minimum drain size allowed. Something a careful review of the IPC venting rules would clear up.

Cheers, Wayne
 

Reach4

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Yes, the IPC only requires a 1-1/2" dry vent for a WC on a 3" drain, and a 1-1/2" wet vent can carry 1 DFU. Add a second lav, or a shower or tub, before the WC, and the minimum wet vent size goes up to 2" at the point where the extra fixtures come in.
He is wet venting the toilets. I think you are saying that the "page 12" of

https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf example only needs 2 inch because there are two lavs feeding the wet vent.
 

wwhitney

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Correct. If the two lavs came in at separate heights, say, then the wet vent between the lavs (carrying just 1 DFU) could be 1-1/2". And the wet vent below both lavs (carrying 2 DFUs) would need to be 2", as shown.

Cheers, Wayne
I missed all this yesterday as I was busy doing demo. So if I read this right I am OK as I am with the 1.5 for both lav drains and vents since they will both be connecting to WC drains (I have not posted the picture yet but I switched the entry point on the upper lav to be before the shower).

This may be irrelevant because I will be opening up this wall today and if I find a 2" vent going through the roof I will likely go with 2" vents and drains for lavs. More capacity never hurts I suppose.
 
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OK, it looks like I will be purchasing materials and getting started on this DWV this weekend ( I got 4 days to work yay).
I have yet to check the size of the vent pipe opening in the roof so my vents may still be changing to 2" rather than 1.5.
The WC in the lower bath ended up being in a really awkward spot and while I didn't have a joist in the way the corner of a CMU foundation pier was. I managed to work out that I can use an offset flange to just barely get clear of it but will have to take it in a different direction than originally planed once under the floor.

If you guys could please let me know if I have any faults with this I appreciate it.
I also have (EDIT) 3 questions.
1. Since the lower bathroom lav stack is so close to wall can I put in an inline cleanout where I show in picture?
2. I will be attempting to keep this system as high as possible to allow me to do encapsulation of crawl space later. the existing system for other bathroom and kitchen is laying on or in the dirt. Is there a rule about doing a 45 degree drop transition from the new 3" to the existing 3" or does it somehow need to be a smooth gradual drop? This is after all pipes come together and it leaves the area to the right.
3. Where does one start with something like this? the longest run to make sure the slopes reach? I am thinking either the lower lav or the upper shower will control the pipe depth.

1668201203654.png
 
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wwhitney

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Looks OK to me. You've drawn most of your combos by showing a short 45 segment, but missed that detail on the tub drain where it joins the lav that is wet venting it.

1) Not sure what you mean by inline cleanout? If you use a trap adapter at the wall under the lav, that should let you snake the whole lav drain, including through the san-tee where the drain turns down to go below the floor. But if you mean put in an upright wye or combo, rolled towards the wall, with a pipe extension that rises into the wall to a cleanout accessible above the floor, sure you could do that.

2) Two 45s are good for a drop in elevation on a horizontal line. If it's a large drop or there are obstructions, you could use two 90s--the top one can be a quarter bend, but the bottom one should be a LT90.

Cheers, Wayne
 
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Looks OK to me. You've drawn most of your combos by showing a short 45 segment, but missed that detail on the tub drain where it joins the lav that is wet venting it.

1) Not sure what you mean by inline cleanout? If you use a trap adapter at the wall under the lav, that should let you snake the whole lav drain, including through the san-tee where the drain turns down to go below the floor. But if you mean put in an upright wye or combo, rolled towards the wall, with a pipe extension that rises into the wall to a cleanout accessible above the floor, sure you could do that.

2) Two 45s are good for a drop in elevation on a horizontal line. If it's a large drop or there are obstructions, you could use two 90s--the top one can be a quarter bend, but the bottom one should be a LT90.

Cheers, Wayne
Well the ones where I showed the short 45 is my attempt at showing the combo that I intend to roll up 45 degrees.
The one there at the tub I was not exactly sure what that fitting will look like...need to check out what is available at HD.

What I meant by the cleanout is just a wye in that pipe under the house with a cap so it can be an additional point of access.
 
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