Bathroom wet vent question

Discussion in 'Plumbing Code Questions' started by mycorrado, Jan 17, 2021.

Joined:
Nov 25, 2020
Location:
Dallas
Hi, I am remodeling a poorly done, garage conversion that has a unvented bath at the end of it.

-Per the picture, I am removing a tub, and installing a shower with the drain and water lines on an interior partition wall (was outside wall before).

-The old lav drain went strait up into the vanity furniture from the floor! I am turning the vanity 90 degrees and moving the drain to an interior partition wall, and . That drain will vent strait up through the roof.

-The toilet is shifting left about 10", I am using two 45's to accomplish this. should be ok right?

Question is if this wet vent scenario work or do I need to vent the shower up into the attic (and attach to lav vent up there) or is it close enough to wet vent.

I would have a mix of both 2" and 3" horizontal drains to get to the vent. Everything currently ties together below the toilet through what looks like a 3" cross.

From the lav drain to the toilet the total distance is 76" (40 x 2"pipe + 36" x 3" pipe) and from the shower drain to the toilet (end of wet vent) it would be 77" (31" x 3" pipe + 46" x 2" pipe)

Would that meet code? Alternatives?

Thanks

File size:
134.8 KB
Views:
42
File size:
129.3 KB
Views:
41
2. wwhitneyWell-Known Member

Joined:
Mar 17, 2019
Location:
Berkeley, CA
I don't see the lavatory labeled on your picture, and I don't quite follow the narrative as to its location. Here's some general comments about horizontal wet venting:

Looks like Dallas follows the IPC. Then what you need is a minimum 1-1/2" lavatory drain (for a single lav; 2" for a double lav with two traps), with a 1-1/2" vent. The lav drain goes under the slab and joins there on the horizontal with either the individual 3" WC drain or the individual 2" shower drain. Then further downstream the other individual bathroom fixture drain joins in on the horizontal.

As to the second photo, I assume you want to move the closet flange to the other end of the opening in the concrete. I'd suggest cutting the horizontal pipe and putting on a LT 90. So taking into account the additional left-right extension of the LT 90 (and the insertion depth of the hub) tells you where to cut the existing horizontal pipe to get the left-right placement of the closet flange where you want it.

As the current pipe appears too close to the wall, you'll need to rotate the LT90 off plumb away from the wall, and then use a bend in the riser to get back to plumb at the correct distance from the wall. Could be 45 degrees rotation off plumb, a pipe segment, and a 45 bend; or more likely I think, 45 degrees rotation and a street 45. Or if even that puts you too far away from the wall, just rotate the LT90 22.5 degrees off plumb and use a 22.5 degree bend to get plumb.

Cheers, Wayne

Joined:
Nov 25, 2020
Location:
Dallas
here is the sink/lav location.

Center of the existing flange is 14 1/2 from the frame so it looks to be to far out. I was going above the minimum 1 1/2 to 2" to get more distance for the wet vent. I am trying to vent the toilet and the shower all from the sink.

File size:
125 KB
Views:
39
5. wwhitneyWell-Known Member

Joined:
Mar 17, 2019
Location:
Berkeley, CA
2" is a fine choice.

I understand the fixture locations now, but I'm not sure I follow the buried piping. Does it run from the lav to the WC to the shower and then to the sewer/septic? If so, that's fine for horizontal wet venting. (And then my discussion about the WC was off, I interpreted the 2nd picture as showing the WC at end of line.)

Cheers, Wayne

Joined:
Nov 25, 2020
Location:
Dallas
No, the new lav runs to where the lav used to be using 2". the old lav runs 3" to a horizontal cross . that cross (4 way) goes out to the left to the sewer, elbows up to the toilet and the 4th goes towards the old tub drain in 3". From there I plan to connect to the new shower drain opposite side.

on the shower I wanted to get fancy and try a linear drain. is there a minimum clearance for the shower drain to the wall?

File size:
26.2 KB
Views:
40
7. wwhitneyWell-Known Member

Joined:
Mar 17, 2019
Location:
Berkeley, CA
OK, the drawing really helps. That's existing, right, and so the WC is moving 10" towards the lav? That means you're going to have to expose and replace the cross, as that point will no longer be a 4 way intersection. [From the small part that can be seen the cross seems to be the wrong part anyway, it should be a double wye or double combo].

Is the 10" figure pretty fixed, or could it be increased to 12" or 15"? Because it's a bit tight there with the fittings to combine the lav and WC, then turn 90 degrees, then bring in the shower.

Cheers, Wayne

Joined:
Nov 25, 2020
Location:
Dallas
Right existing. I was hoping to use much of what's down there, but I see that cross isn't right. I am not set on 10", just wanted to get the toilet a little further away from the shower glass. it currently sits at 15, with the lateral 45's I get to 19". if I change the cross I can do like you suggested and put a 90, at a slant and bring it up with the right bend to get another 5 ish. Would this wye work?

File size:
135.1 KB
Views:
36
File size:
28.4 KB
Views:
36
9. wwhitneyWell-Known Member

Joined:
Mar 17, 2019
Location:
Berkeley, CA
That last picture is a double fixture fitting, also only used vertically. You'd need a double combo fitting, or a double wye fitting.

I had been thinking of joining the WC and the lav along the horizontal pipe going parallel to the wall. But if you want to use a double fitting, you could do it like this (be sure to read postscript at the end):

First check to see if using a double combo fitting would work. [Edit: this is a thought exercise, as you really need to use a double wye instead. See the following post for details.] Given the double san-tee that's in there now, the shower and lav drains should be in line with each other, but if one of them is slightly angled as it enters the double san-tee, the greater spread of the side entries of the double combo might cause a problem.

The other thing to check is the distance from the wall for the WC. Going into the straight inlet of the double combo, you have a choice of street medium turn 90 ; street long turn 90 ; short pipe segment and regular medium turn 90 ; or short pipe segment and regular long turn 90. Those are listed in increasing order of the distance from the wall the toilet flange will end up. So if one of those will get you to 12-1/2" or close enough, the double combo would work. [Normally a vertical to horizontal turn is required to be a LT90, but a "closet bend" is a tighter turn, that in plastic at least matches a medium turn 90 (regular quarter bend). So you can use either directly under a WC, although LT 90 would be preferred if the space is available.]

If the double combo doesn't work for either of those reasons, you can use a double wye. That lets you adjust the three inlets independently, by moving the double wye towards the wall, and using a longer or shorter pipe segment between the inlet and the next fitting.

Finally you can set the left right location of the WC by turning the 90 coming out of the double fitting 45, 60, or 67.5 degrees off plumb, using a short pipe segment, and then a 45, a 60, or a 45 + 22.5 to get back to plumb. Whatever you need to get the left-right placement you want while keeping the closet flange at the correct elevation.

Cheers,
Wayne

P.S. I realized that if you turn the 90 more than 45 degrees off plumb, that 90 is now a horizontal to horizontal change of direction, and it definitely has to be a LT 90. So if you need to turn it more that 45 degrees to get your left-right placement correct, that would limit your options on the double fitting placement for getting the distance correct off the wall. Which means the two layout considerations are interrelated and you'll have to consider them both at the same time.

Last edited: Jan 17, 2021
10. wwhitneyWell-Known Member

Joined:
Mar 17, 2019
Location:
Berkeley, CA
P.P.S. There is a geometrical concern to using a flat double wye fitting, which is that when both side inlets are at the same elevation, the slope on the branch inlet is only 70% of slope on the straight path of the fitting. [And for a double combo fitting, the inlets would be level, so double comobos should not be used on the flat.]

How much this matters is subject to debate, and various jurisdictional decisions on the matter have been posted here in the forum in the past. Dallas is I believe on the IPC, meaning a 3" drain is allowed to have only 1/8" per foot slope (though I would say that a 1/4" per foot is better).

So if you have at least 1/4" per foot slope on the straight path, your branch inlets would have over the IPC minimum slope, and I wouldn't be concerned. Conversely, if you have only 1/8" per foot slope on the straight path, then I at least would be concerned. The concern is only for the pipe segment between the side inlet on the wye and the next 45, as that 45 can be rotated up a bit to give the necessary slope.

The only way around this issue is to use two separate wyes in series, so that each side inlet can have its slope set separately. And if it comes to that, I would suggest also considering instead using a LT90 and a wye, and joining the lav to the WC on a pipe segment parallel to the wall (or possibly 45 degrees from the wall).

Ultimately, this will all be determined by the elevation difference between the ends of your three pipes (lav, shower, and drain to the sewer) after you cut out the double san-tee. In the worst case, where the elevations are identical and everything would be flat, the proper solution is to raise the lav and shower drains, which would require cutting more concrete or some careful tunneling.

Cheers, Wayne

Joined:
Nov 25, 2020
Location:
Dallas
well I'm back.

I am actually in Coppell but Dallas county. here they use UPC.

I can't connect two fixtures into a horizontal wet vent at the same time. I see two options I think meet code?

Option A, Vertical wet vent: the toilet and shower are wet vented between the flange and the closet elbow via a 4"x3" Double San Tee.
This option is a tight fit, but I think I can get the slopes right into the san tee as the distances are about the same.

Option B, I go horizontal wet vent with the Branch perpendicular to the exterior wall and separate Y's for the vent source, shower and Toilet.
This requires a lot more concrete busting.

Pardon my very crude drawings

File size:
120.2 KB
Views:
32
12. wwhitneyWell-Known Member

Joined:
Mar 17, 2019
Location:
Berkeley, CA
Why is that?

Cheers, Wayne

Joined:
Nov 25, 2020
Location:
Dallas
I got confused, was reading IPC.. too many tabs open. IPC 912.1.1 doesn't apply to me.

I'll go back to your suggestion and draw it out to make sure I understand it right. thanks!

Last edited: Jan 19, 2021

Joined:
Nov 25, 2020
Location:
Dallas
Wayne, Do I understand your original suggestion correctly?

File size:
96.9 KB
Views:
35
15. wwhitneyWell-Known Member

Joined:
Mar 17, 2019
Location:
Berkeley, CA
Basically yes.

In considering it again, I think it is important to use a LT90 at the straight inlet of the double wye. So hitting 12.5" off the rough wall is achieved by the placement of the double wye and the choice of street LT90 or regular LT90 with a short pipe segment in between.

And the choice of rotation off plumb of the LT90 and length of pipe segment before using a bend to go plumb determine the left/right placement. I suggest 45 degrees off plumb if that will get you far enough to the left without the 45 bend ending up too high in the slab.

Lastly, UPC requires 1/4" per foot slope on 3" drains. So I would suggest trying to pitch the barrel of the double wye at 3/8" per foot. That way the side inlets are slightly over 1/4" per foot. Whether you can do that without raising the lav and shower drains depends on what elevation difference you currently have.

Cheers, Wayne