Vent and drain configuration - Wisconsin

[Mke_Nate]

Long-time reader, first-time poster here. The questions others have asked here has been very helpful as I've worked on our bathroom project. Any guidance or comments are greatly appreciated!

Background: we're working on a to-the-studs remodel of our main floor bathroom. It was original to 1929 and had odd design quirks, such as 8" clearance from the rim of the toilet to the bathtub. This has caused us to rearrange all the fixtures in the room to meet modern code and to be more functional.

Hence the question and advice: What's the best way to tie into the main 4" drain/vent stack? Today, the toilet drains into an integral cast iron fitting. That has to go, as does the drum trap for the bath tub. The tub is out, we're down to the studs, and now we're onto replumbing.

We won't finish our basement. The area where the proposed plumbing would be placed is in utility space shared with the water heater, furnace, and other utilities.

Plan ideas:

Here's a plan view under I'm consideration. The distance from the centerline of the closet flange to the heel elbow is about 36" I'm considering running a horizontal run along the basement wall shown in the diagram below.

Here is an elevation view of what we're considering. I plan to run a 2" vent from the 3x3x2 heel fitting back to the stack, and tie in the 2" line coming from the tub and sink. In this plan, I would tie into the stack using a 4x4x3 wye and a 45 degree fitting to get the pipe vertical. Slope is shown exaggerated below. I plan to add a clean-out on the 3" line that runs mainly horizontal at the left side of the page:

The other option I drew up gives me some concern. I sketched something up that would use a 4x4x3 sanitary tee to tie the leg from the water closet into the stack. I'm not too keen on this one, especially considering the run length from the 4" soil pipe/stack to the closet flange is around 8'. I like option B less.

 

[wwhitney]

The main problem with option A is that a dry vent takeoff has to be vertical and stay vertical until 6" above the fixture flood rim. Your WC vent in option A does not do that. Also, I'm not 100% clear on the tub vent geometry, whether it complies or not.

Option B seems simpler to me, and it would wet vent the WC. The connection at the stack could be a san-tee or a wye (combo). You probably could eliminate the tub vent and wet vent the tub as well. For the details on that, you'll need to check Wisconsin's plumbing code, if I recall it's non-standard. For a UPC bathroom group wet vent, you'd use a 2" lav vent, a 2" lav drain, and have the lav drain join the tub trap arm before it joins the WC.

Cheers, Wayne

 

[Sponsor]

 

[Mke_Nate]

Thanks for your quick response, Wayne. I completely overlooked the flood rim requirement when drawing Concept 1. It's one of those sketches that got just a little out of hand...

I'll stew on the Wisconsin code and study the wet venting allowance and put together an updated sketch.

Cheers,

Nate

 

[Mke_Nate]

Below is my second attempt at putting together a code-compliant plan.

Re-reading the Code below, I think this design meets the requirements. The bathroom is residential, the wet vent serves a single water closet and bathtub, and each of the fixtures (lav sink, tub, and closet) connect independently to the wet vent.

The third concept is significantly less complicated than the first one and should be a lot easier (and less expensive to plumb).

Best,

Nate


For reference, here's the relevant section from the Wisconsin plumbing code (SPS 382.31(13)):

(b) Horizontal wet vents. A drain from a lavatory or lavatories which are either provided with individual vents or a common vent may serve as the wet vent for not more than 2 bathtubs or showers and not more than 2 water closets in accordance with subds. 1. to 7. No other fixtures may discharge into or be served by the wet vent.
1. All of the fixtures shall be located in nonpublic bathroom groups.
2. The lavatories and bathtubs or showers shall have a common horizontal drain with the drain for the lavatories serving as a wet vent for the bathtubs or showers.
SPS 382.31(13)(b)3.3. Where 2 bathtubs or showers are served by the same wet vent, their fixture drains shall connect independently to the common horizontal drain downstream of the vertical drain serving the lavatory or lavatories.
4. Where 2 bathtubs or showers and 2 water closets are served by the same wet vent a relief vent shall be provided, unless the wet vented horizontal drain connects to a drain stack with no other drain connections located above the wet-vented horizontal drain. The relief vent shall connect to the horizontal drain at a point downstream of the fixture drains for the water closets and upstream of any other fixture drain connections.
5. One or 2 water closets may connect to the common horizontal drain with the drain from the lavatories and bathtubs or showers also serving as a wet vent for the water closets. Where 2 water closets are served by the same wet vent, their fixture drains shall connect independently to the common horizontal drain at the same point.
6. The wet vent shall be at least 2" in diameter. No more than 4 drainage fixture units may discharge into a 2" diameter wet vent.
7. A branch vent shall connect immediately above the highest fixture drain connection and shall be sized in accordance with sub. (14).

 

[wwhitney]

I agree it complies with the quoted wet vent rules. If you are going to use a 2" tub trap arm, I would use a 2" tub trap. Or stick with a 1-1/2" trap and use a 1-1/2" trap arm, if that complies with the WI trap arm length limits. [Just to double check, the total fall from the tub trap outlet to the 3" wye is limited to one pipe diameter.]

Cheers, Wayne