Bathroom remodel, drain/vent design

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Webdood90

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Hi there. I'm planning to redo all of the plumbing in my upstairs bathroom. The drains and vents are the part I'm least confident in doing correctly. I'm in Denver which uses IPC.

Below is a picture of my current plumbing and the changes I would like to make. There is currently one vent for everything in the bathroom - plus a laundry drain, which doesn't seem correct.

My current plan:
- align 3 inch with toilet, 45 to main stack at bottom left
- 3x2 45 wye to vanity
- 2x1.5 45 wye to vent rolled up
- vanity drain continues to long turn 90 to ptrap
- 3x2 double 45 wye to laundry and shower
- on laundry side, 2x1.5 45 wye to vent rolled up
- laundry drain continues to long turn 90 to ptrap
- on shower side, similar to laundry
- to toilet, 3x2 45 wye to vent rolled up
- toilet would use 4x3 closet bend

All drains would meet 6 inches above top of vanity bowls, each connecting at a 45 on a common vent until they reach the 2 inch main vent in the corner which exits the roof.

Would this be acceptable?
 

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wwhitney

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Your proposed layout is not going to work. Is the laundry a standpipe or a laundry sink? Let's start at the beginning:

Except for the WC, each trap (lav, shower, laundry) needs to have a vent connection to its drain before (dry vent) or as (wet vent) it connects to another drain, and before it has fallen more than one pipe diameter. So as the lav trap and laundry trap are above the floor, their vent connections will be above the floor.

Now the dry vented lav can wet vent the shower and the WC. The typical way to do that is to join the lav drain to the shower drain (before the shower drain falls more than one pipe diameter), and then join the shower/lav to the WC. The IPC allows the opposite order, where the lav joins the WC first, and then the shower joins. Either way, if you are wet venting, the laundry has to come in after all the bathroom fixtures, as the laundry can not participate in the wet vent.

A few more considerations: dry vents have to come off the drain on the vertical (which includes up to 45 degrees off plumb) and stay vertical to 6" above the flood rim of the fixture. For the shower and the WC, that can be challenging (easiest is to pass the drain under a wall for a dry vent takeoff), so wet venting them is simpler. Also, if your laundry is a standpipe, then the IPC requires that when the laundry drain joins another drain, the combined drain is at least 3".

That should be enough guidance for you to come up with another layout. Also, a somewhat wider view picture would help, or a diagram.

Cheers, Wayne
 

Webdood90

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Wayne, thank you for your guidance. I really appreciate it.


A few clarifying questions because I'm new to this:

"...before it has fallen more than one pipe diameter" - Using my lav as an example, I would need to vent it within 2 inches after the P trap? Using the shower as an example, I would have about 4 feet after the P trap to vent it? (thinking 1/4 fall per foot) Or am I misinterpreting that?

The lav is on a wall that is in the center of the house, so I don't believe I can vent straight up and out. Ideally, I can route it all through the vent in the corner.

With what you described, it sounds like I can possibly connect the lav to the WC, shower to the lav, and vent off the shower instead (lav and WC are then wet vented, correct?). That would allow me to run the vent rolled up to the wall at the top of the picture, right?

I'll work on a diagram after work, but have attached additional pictures that I have in the meantime.
 

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wwhitney

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"...before it has fallen more than one pipe diameter" - Using my lav as an example, I would need to vent it within 2 inches after the P trap? Using the shower as an example, I would have about 4 feet after the P trap to vent it? (thinking 1/4 fall per foot) Or am I misinterpreting that?
The pipe from the trap outlet (the elbow part) to where the vent attaches is called the trap arm. That trap arm, like all drainage under 3" in size, needs to fall at least 1/4" per foot. If you want to get the longest possible trap arm, then it needs to fall at exactly 1/4" per foot. That gives you the IPC allowable trap arm length based on trap size, and the "fall no more than one pipe diameter" rule: 1-1/4" trap = 5', 1-1/2" trap = 6', 2" trap = 8'. But the total fall is the real limit, if your 2" trap arm is falling at 1/2" per foot for some reason, it can only be 4' long.

Best practice is to use 2" for the shower, rather than 1-1/2". But the IPC allows 1-1/2" for showers with heads totaling no more than 5.7 gpm.

The lav is on a wall that is in the center of the house, so I don't believe I can vent straight up and out. Ideally, I can route it all through the vent in the corner.
Once a vent is 6" above the flood rim of any attached fixtures, it can go horizontal. So you can have your vent(s) rise up within that wall, and then go to the corner if that's where they need to be before rising further. With the horizontal run either in the wall or in the joists above.

With what you described, it sounds like I can possibly connect the lav to the WC, shower to the lav, and vent off the shower instead (lav and WC are then wet vented, correct?). That would allow me to run the vent rolled up to the wall at the top of the picture, right?
If you are trying to minimize dry vents, which have to rise up to the roof (or under the IPC, to an AAV, although the roof is preferred when possible), then you need to start with a dry vent at the lav (its trap is highest). The lav drain can go on to wet vent the WC and shower. So only one dry vent takeoff for the 3 bathroom fixtures. The laundry standpipe will need its own dry vent, and of course the kitchen sink needs a dry vent.

Cheers, Wayne
 

Webdood90

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Thanks, Wayne. I've attached an updated layout (inside rectangle is the floor, outside is the walls). I messed up the fitting where the laundry drain meets the WC, should be a 45.

Assuming everything with this is okay, my only concern is the vent from the lav. There is a window on the right wall that I'd have to clear, which is higher than where the vent exits the roof in the corner. Perhaps I could get away with an AAV here instead.

Also, the vent for the laundry drain needs to bend around an old chimney before it can run to the corner to meet the main vent, like so:

20220128_175741.jpg

Looking at the code, it doesn't seem like there are restrictions for movement like this as long as it lets condensation fall back to the drain, but I wanted to make sure that's not an issue.

Again, can't thank you enough for taking a look. I'd love to buy you a beer at the very least if you'd let me PayPal or Venmo you.
 

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wwhitney

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No problem jogging the vent around the chimney like that, just pitch everything back to the drain at 1/4" per foot slope.

As to the window and the lav vent, below the window is too low (less than 6" above the lav flood rim), and above the window is too high, higher than where the Main Vent exits the roof? The IPC arguably allows a vent to be pitched to any drain, not just the drain it serves, so you could put a kink in the vent where the high spot is over the window and the side between the window and the main vent drains down to the main vent. That's sufficiently weird that I'm not sure I'm recommending it. You could, of course, penetrate the roof separately, with the incumbent hassle.

Your drawing format is interesting if non-standard. It's basically taking a 5 sided box and folding the walls down flat. I think it would be clearer if it was just a cross-shape (floor, 4 walls) and pipes just jumped (on the page) from one wall to the next, with maybe letters or dashed lines to show the connectivity.

Anyway, the connectivity you drew works. It's a little unfortunate the lav drain has to do 270 degrees of turn in the floor system to meet the Main. Depending on which way the joists run, and the distances involved, you could consider putting the left-right (on the page) lav drain section in the floor closer to the main at the bottom of the page, maybe even lined up with it. The shower drain could run towards the lav wall and hit a LT90 to hit that left-right (on the page) lav drain section. And perhaps the laundry drain just continues down the page and hits the Main, letting the WC hit the Main between the lav/shower and the laundry. But maybe there are some structural/access reasons that preclude those simplifications.

BTW, in the wall you've drawn the vent takeoffs as not aligned with the vertical drains. That's fine, you can do that, just use an upright combo for the vent takeoff, and then a quarter bend for the drain to turn down. But if lined up works for you, then you can just use a sanitary-tee, that's what it's for.

Cheers, Wayne
 

Webdood90

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As to the window and the lav vent, below the window is too low (less than 6" above the lav flood rim), and above the window is too high, higher than where the Main Vent exits the roof?
Correct

The lav vent suggestion is along the lines of what I was thinking. What if it just ran vertically to the ceiling, ran directly across in the attic, and then pitched downwards to meet the laundry vent? So I wouldn't run it through the right wall at all.

Apologies for the odd format, I wasn't sure how best to illustrate the design but glad you were able to interpret it.

Is this what you had in mind for the simplifications? The lav/shower 2" could connect to the 3" main above the 45? This seems much cleaner, if correct. There is actually a drop ceiling in the kitchen below, so I'm not restricted to just the joists which makes this easier.

20220128_220834.jpg


But if lined up works for you, then you can just use a sanitary-tee, that's what it's for.
That sounds easier, I'll update my plans.
 

wwhitney

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So, on the laundry vent, the issue is that the room doesn't have ceiling joists (or has ceiling joists that are raised above the exterior wall top plate), and so the lowest you can transit the lav vent across the ceiling is too high to connect to the laundry vent underneath the roof, unless it dips down at the end? I hesitate to offer an opinion on whether the dipping down at the end is OK, beyond the observations that I've already made. Here's the relevant portion of Colorado's code:


I assume that you've considered running the vent pipe the other way around the walls (opposite the way that hits the window) and that also doesn't work without a dip?

Yes, the diagram matches what I described (the right angles are LT90s or combos), but I don't follow the comment "The lav/shower 2" could connect to the 3" main above the 45." As rendered I would expect all the lines to be horizontal at 2% slope (1/4" per foot). But the only part where the slope is critical is from the shower trap to where the lav drain joins in a combo, the shower trap arm can only fall one pipe diameter. The rest of it could be sloped well over 2% if necessary.

Cheers, Wayne
 

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So, on the laundry vent, the issue is that the room doesn't have ceiling joists (or has ceiling joists that are raised above the exterior wall top plate), and so the lowest you can transit the lav vent across the ceiling is too high to connect to the laundry vent underneath the roof, unless it dips down at the end?
Correct

I hesitate to offer an opinion on whether the dipping down at the end is OK, beyond the observations that I've already made
Okay, no problem. I'll see if I can contact my inspector about it to be sure.

I assume that you've considered running the vent pipe the other way around the walls
Yeah, there is a door on that side that poses a similar problem.

I don't follow the comment "The lav/shower 2" could connect to the 3" main above the 45."
Sorry, I used poor language to describe that. Basically, from the shower trap to the main would all remain 2" and I'd use a 3x2 to connect there, just right of the 45 which goes to the WC. This is probably obvious but wanted to confirm.

Thanks!
 
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Webdood90

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Preparing to buy materials, finally. Hoping for a last-minute sanity check. After reviewing my joists and the positioning of drains, my layout will be as attached.

Still waiting on confirmation from the inspector about venting the toilet, shower, and lav with the AAV.

1. Laundry - 3x2 45 wye up vertical, then 45 elbow, then 90 from that to horizontal towards drain
2. Toilet - 3x3 45 wye up vertical, then 45 elbow, then 90 from that to horizontal towards drain
3. Lav/Shower - 3 to 2 reducer
4. Shower - 2x2 45 wye up vertical, then 45 elbow, then 90 from that to horizontal towards drain
5. Lav - long turn 90 elbow

Is it correct that I cannot use a 90 in place of the 45 wye + 45 elbow?

Thanks!
 

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wwhitney

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(4) is wrong. From the shower trap to the 2" wye lav connection where the trap arm is vented, the total fall can be no more than 2" (the trap diameter). So the 2" wye must be horizontal, with only horizontal elbows between the trap and the wye.

At (1) and (2) the extra fall is allowed (1 is a vented drain and for 2 the trap weir rule doesn't apply to WCs) and your configuration works. (You can get a wye plus 45 cast as one piece, called a combo, that's fine to use). But you often don't need the 45 degree elbow. You can just roll your quarter bend (LT90 not required) 45 degrees so the outlet points at the wye. Assuming the height change you need is not that large, and that you have room within the joist bays for that.

Cheers, Wayne
 
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Webdood90

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Thanks, Wayne! I will make that adjustment.

I think I got the sanitary tee confused with a combo and read that it could not be used when horizontal, so that will make things more simple.

One other question - in preparation for an inspection, I've seen that people install test tees just before the connection to the old drain so that it can be stopped and water tested. That makes sense, but does this test tee need to be accessible after the project is complete and walls/flooring are in place? I ask because that would not work with the arrangement I have, so I'm wondering how to accommodate.
 

wwhitney

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Good question. I've not actually had that come up, hopefully one of the full time plumbers can answer.

I would think if it is allowed to be buried, and it's on a horizontal drain section, then you'd want the tee opening facing up.

Cheers, Wayne
 

Webdood90

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Had to adjust my plans a bit once I started laying pieces down, will post pictures shortly.

Semi-good news is that I discovered another vent in a different wall from a half bath below. It's 1.5 inch and would allow me to run my lav vent across the ceiling to connect to it. My question is whether 1.5 inch is enough to vent the double lav, shower, toilet, and the laundry.

I don't have to connect the laundry, I can still use the kitchen vent I originally planned on, but I think it would be easier.

I referenced the table in section 906 of IPC and believe it will work, but I'm wondering if the fact that I'm wet venting the shower and toilet changes that at all.

Screen Shot 2022-02-15 at 10.57.34 AM.png
 

wwhitney

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My question is whether 1.5 inch is enough to vent the double lav, shower, toilet, and the laundry.
My understanding for the IPC (in use in CO) is yes. That the dry vent is connected to a wet vent doesn't alter the dry vent sizing. The wet vent of course has its own sizing, but 2" is sufficient for a wet vent carrying 4 DFUs of drainage (the shower and both lavs).

Cheers, Wayne
 

Webdood90

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Meant to post some updates on this. Still waiting on a piece for my shower wand.

Couple things I want to change after thinking on what I've done:
- Pull the laundry supply lines off the exterior wall. Hardly an inch behind them now for insulation which I can't imagine is going to pass inspection. I don't know what I was thinking originally.
- Have a custom shower arm fabricated to run on top of the tile. Same as the laundry lines, running in the slanted ceiling cavity which isn't going to allow much insulation. Not sure where to go about finding something like this or how to make it myself.

Hopefully nothing too terribly wrong with what you see here. First time doing this so it's not the cleanest install.
 

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