Venting question - new build

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David S

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I think I have two ideas on venting a bathroom but wanted some professional feedback!
It's a new home that is a stilt home so 10 ft off the ground, 2x12 floor joists that I am keeping the branch drain lines within that space. I have a 4' drain below the floor joists running down the middle of the home. I have realized now I am a horrible artist but see my attached picture. Sink is on the right hand side with 2"vent, toilet is in the middle with a 3" drain line and bathtub is on the left side. I had two plans, one is run a 2" or 1 1/2" pipe off the toilet and shower drains with a wye fitting at a 45' degree angle up back to wall and tie into 2" vent.
The other is to run a vent back to the wall for the shower drain and tie into my vent and bring that shower drain through the joist and tie into 3" toilet drain. I believe this would wet vent the toilet through the shower line and vent. If I'm missing an easier or better way please let me know. I was trying not to put holes in joists or do the least amount of holes as possible. See attached sketch (not an artist for sure!!) and pics of space.
1661485457316.png

1661485491275.png
 

wwhitney

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IPC or UPC? You can wet vent both the tub and the WC using the dry vented lav drain, but the IPC offers you a little more flexibility on the details.

With 2x12 joists, it's really not a problem to drill a 2-3/4" or 3" hole for a 2" drain, out of the 11"+ depth you can drill it anywhere in the central 7" (leave 2" clear top and bottom). You could even drill a 3-3/4" hole in a 11-1/4" deep joist for a 3" drain, but it's nice not to have to.

Cheers, Wayne
 

David S

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IPC or UPC? You can wet vent both the tub and the WC using the dry vented lav drain, but the IPC offers you a little more flexibility on the details.

With 2x12 joists, it's really not a problem to drill a 2-3/4" or 3" hole for a 2" drain, out of the 11"+ depth you can drill it anywhere in the central 7" (leave 2" clear top and bottom). You could even drill a 3-3/4" hole in a 11-1/4" deep joist for a 3" drain, but it's nice not to have to.

Cheers, Wayne
Thank you for the reply Wayne! It is IPC here. Good to know on drilling through joists. I attached 3 scenarios. Would either of these work? I think I would prefer the 3rd as it would be easier for me to do more work inside then outside on a ladder. Again, thank you for the knowledge and time!!
 

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wwhitney

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(2) is the simplest of those and works for the IPC (but not the unamended UPC).

(1) is problematic because a double wye shouldn't be used horizontally, successive single wyes let you adjust the branch inlet slopes independently, which you can't do with a double wye.

(3) is tricky because of the diagonal portion drawn below the shower. That's the dry vent takeoff, and it needs to be "vertical" which means up to 45 off plumb. So the dry vent would have to be rising in the floor while it runs back to under the wall, and it can be hard to keep it from rising through the subfloor before it hits the wall. But it is certainly possible.

A few further comments: the lav drain doesn't have to enter the floor system directly below the san-tee for the sink. It could turn horizontal and enter the floor system in a more convenient location, as far as wet venting the other two fixtures.

The IPC would allow the lav drain and vent to be 1-1/2" rather than 2"; UPC requires 2".

I assume the 4" line is running under and perpendicular to the joists, while the 3" line is higher within the joist bay? If so, since you don't show the details of that connection, you could use a 3" quarter bend, rolled so it's outlet is 45 degrees off plumb, directly into a 4x4x3 wye with the barrel horizontal and the side branch upright.

Cheers, Wayne
 

David S

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(2) is the simplest of those and works for the IPC (but not the unamended UPC).

(1) is problematic because a double wye shouldn't be used horizontally, successive single wyes let you adjust the branch inlet slopes independently, which you can't do with a double wye.

(3) is tricky because of the diagonal portion drawn below the shower. That's the dry vent takeoff, and it needs to be "vertical" which means up to 45 off plumb. So the dry vent would have to be rising in the floor while it runs back to under the wall, and it can be hard to keep it from rising through the subfloor before it hits the wall. But it is certainly possible.

A few further comments: the lav drain doesn't have to enter the floor system directly below the san-tee for the sink. It could turn horizontal and enter the floor system in a more convenient location, as far as wet venting the other two fixtures.

The IPC would allow the lav drain and vent to be 1-1/2" rather than 2"; UPC requires 2".

I assume the 4" line is running under and perpendicular to the joists, while the 3" line is higher within the joist bay? If so, since you don't show the details of that connection, you could use a 3" quarter bend, rolled so it's outlet is 45 degrees off plumb, directly into a 4x4x3 wye with the barrel horizontal and the side branch upright.

Cheers, Wayne
Thank you very much Wayne! Makes sense on everything you said. I’m thinking I’ll have the sink drain run horizontal over to the vent which I’ll put to closer to the toilet like pictured below.
 

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Jeff H Young

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only thing I dont like is drilling through joist on a 45 oblonging the hole but looks good to me too.
 

wwhitney

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Thank you very much Wayne! Makes sense on everything you said. I’m thinking I’ll have the sink drain run horizontal over to the vent which I’ll put to closer to the toilet like pictured below.
That does simplify things, particularly if you can get the lav drain to enter the floor system in the same joist bay as the WC. The lav trap arm can be 1-1/2" in the wall, so that way you don't have to drill the wall studs for a 2" pipe. The 1-1/2" trap arm, if you use a 1-1/2" trap under the lav, can be up to 6' long (summing both in the wall and under the lav) and drop up to 1-1/2" in total.

Jeff has a good point on drilling the joist at a 45, a bit difficult to do (but feasible) and possibly weakens the joist more than drilling at a 90 (not sure, that would require some more thought to determine). If the shower drain and closet flange are in adjoining joist bays, I'd be happy to do that for one joist. If they are two or more joist bay apart, you might just want to turn the shower drain to be perpendicular to the joists and use a combo where where the shower drain hits the WC drain. [That connection has to be downstream of where the lav hits the WC drain for proper wet venting.]

Cheers, Wayne
 

Jeff H Young

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eliminating the wye for tub and where wet vent 90s up wall imediatly above longsweep a 2 x2 x1/12 santee could serve tub, point it away from wall with a 45 drill one joist straight for the trap arm. thats another idea! a santee cheaper than a 3x2 wye too.
you got good plan though
 

wwhitney

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eliminating the wye for tub and where wet vent 90s up wall imediatly above longsweep a 2 x2 x1/12 santee could serve tub, point it away from wall with a 45 drill one joist straight for the trap arm. thats another idea! a santee cheaper than a 3x2 wye too.
you got good plan though
Sorry, not sure I follow your description.

Are you saying that were the lav drain goes down through the plate into the floor system, have a san-tee high in the joist bay to vertically wet vent the tub, and then have an immediate (street) LT90 to turn horizontal, to then join the WC drain to wet vent it? That would work if the 11"+ joist bay is tall enough for everything to fit vertically and for the elevation of the 3" line in the joist bay would not be too low when it ultimately hits the 4" line (which I presume is below the joists).

Cheers, Wayne
 

Jeff H Young

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Sorry, not sure I follow your description.

Are you saying that were the lav drain goes down through the plate into the floor system, have a san-tee high in the joist bay to vertically wet vent the tub, and then have an immediate (street) LT90 to turn horizontal, to then join the WC drain to wet vent it? That would work if the 11"+ joist bay is tall enough for everything to fit vertically and for the elevation of the 3" line in the joist bay would not be too low when it ultimately hits the 4" line (which I presume is below the joists).

Cheers, Wayne
yes Wayne thats what Im talking about. the 4 inch main could be a few feet away or 20 I wouldnt know. santee might be too high ? you can also instead of a using a long sweep use a 45 the santee , and then another 45. just throwing a few ideas out .
I pressume he isnt drilling out all the joists for the 4 inch main as well, he could be far below running along a beam or other senarios too.
 

wwhitney

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santee might be too high ? you can also instead of a using a long sweep use a 45 the santee , and then another 45. just throwing a few ideas out .
That works if the shower/tub drain can approach the san-tee perpendicular to the joists. But the downside to that line of approach is that if there's a wall both above and below the joists there, the joist ends up in vertical compression in that region and it isn't a good place to drill for a drain. But if there's just a wall above and no wall below, that may not apply, I'm not sure.

Cheers, Wayne
 

Jeff H Young

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solid wood joists no issue manufactured truss joists valid point you dont drill those on the ends.
 

wwhitney

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solid wood joists no issue manufactured truss joists valid point you dont drill those on the ends.
I disagree a bit on the solid wood joists. Not seeing anything in the Residential Code that directly address this, but there is a requirement for 1-1/2" of joist bearing. And I'd see a hole over a bearing wall as reducing the bearing width.

From that point of view, a 2" hole over a 2x4 wall would be OK, but larger would reduce the bearing too much. Maybe not explicit in the code language, but I think valid from an engineering point of view. Of course, for the 45- santee- 45 you suggested, that might kick the hole out so it's not fully over the wall, and leave sufficient bearing even after a 2-3/4" hole.

As to I joists, agreed. An I-joist alone is not used to transfer vertical load from a wall above to a wall below. The I joist would need to have squash blocks, and you wouldn't want to drill the combo squash block/I-joist.

Cheers, Wayne

 

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I disagree a bit on the solid wood joists. Not seeing anything in the Residential Code that directly address this, but there is a requirement for 1-1/2" of joist bearing. And I'd see a hole over a bearing wall as reducing the bearing width.

From that point of view, a 2" hole over a 2x4 wall would be OK, but larger would reduce the bearing too much. Maybe not explicit in the code language, but I think valid from an engineering point of view. Of course, for the 45- santee- 45 you suggested, that might kick the hole out so it's not fully over the wall, and leave sufficient bearing even after a 2-3/4" hole.

As to I joists, agreed. An I-joist alone is not used to transfer vertical load from a wall above to a wall below. The I joist would need to have squash blocks, and you wouldn't want to drill the combo squash block/I-joist.

Cheers, Wayne

I didnt mean to imply notching joist directly below wall was good idea point santee away from wall on a 45 degree then install a 45 slightly past the edge of wall and youll be in perfect alighnment with the waste and over flow of tub for standard joists only .
drill hole 1/3 the size of joist withen first 3rd of span should fly by drilling wher I said. differant rules on truss joists
 

wwhitney

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point santee away from wall on a 45 degree then install a 45 slightly past the edge of wall and youll be in perfect alighnment with the waste and over flow of tub for standard joists only
That's all good, but you can only "point the san-tee away from the wall at a 45 degree angle" (in plan, i.e. as seen from above) if you go with a san-tee then LT90. If you go with 45 - san-tee - 45 then you are stuck with the san-tee pointed perpendicular to the joists.

I.e. both are good options, just not ones you can use together. That was my only point.

Cheers, Wayne
 

David S

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Thank you for the ideas and help! I’ll move the drain line over from the sink as suggested and if I have room for the shower tie that in to the vent as well. My 4” drain is about 8’ away and hangs under the floor joists. Thank you again!!
 

Serkan

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I am having a similar situation with my bathtub venting. Trying to dry vent it back to the plumbing wall.

I made a thread asking about a p-trap and trap arm-vent setup but not sure if it is to code.

Since you have 2x12 floor joist, you can drop tub p trap further down and easily make it to the plumbing wall.
 

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Jeff H Young

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I am having a similar situation with my bathtub venting. Trying to dry vent it back to the plumbing wall.

I made a thread asking about a p-trap and trap arm-vent setup but not sure if it is to code.

Since you have 2x12 floor joist, you can drop tub p trap further down and easily make it to the plumbing wall.
Serkan , that works not sure if canada allows 1 1/2" line to tub mycode calls for 2 inch drain downstream of trap arm , trap arm 1 1/2" is ok , venting is perfect.
 

David S

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That works if the shower/tub drain can approach the san-tee perpendicular to the joists. But the downside to that line of approach is that if there's a wall both above and below the joists there, the joist ends up in vertical compression in that region and it isn't a good place to drill for a drain. But if there's just a wall above and no wall below, that may not apply, I'm not sure.

Cheers, Wayne
Ok, last bathroom for me to figure out. See pic below. I’ll have double vanity, toilet next to shower and shower stall. Please critique my thoughts. Double vanity will be 2” drain and vent, will run it 90 degrees through one joist to bring it to my 3” toilet drain via a wye. That will be my wet vent for the toilet. I’d like to make a vent for the shower that I can tie into the sink vent above but not sure how to vent the shower separately. Blue lines are my vents. Just trying to run one 2” line from my shower to my main line so it’s easier but need some thoughts on that. My 4” line is about 10 ft away from the toilet. Thank you again for the help!!
 

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