Wet vent and new shower drain

[Cherrie]

Hello everyone,

I need some assistance with a new shower drain in a tub/shower to shower only conversion I’m doing in my master bathroom. I tore out the garden tub, gutted the room and replaced the floor (and then pulled some of it back up to access the plumbing as you can see in the photos). One photo provides a close-up of the plumbing that needs to be altered and I included the other two photos to give you a visual of how everything is laid out. The shower drain is what I need help with specifically but I'm open to advice and/or suggestions for additional improvements - I'm sure you'll understand why once you've had a moment to study the photos and are able to evaluate my less than stellar bare minimum plumbing system which was apparently designed by someone sorely lacking in common sense and who, rather than make an effort to design a plumbing layout that took the existence of floor joists and other rather important items into account, chose instead to focus his highly questionable skills on making one that could be assembled with the least amount of materials humanly possible because hey, who cares if the toilet flange is centered 15 inches from wall, right?

No doubt most of you have already figured out this is a manufactured home and you're right – it is - and I deeply apologize for that but I'm stuck with it so what can I do? (This is where you cheer me up and say "No problem, we got this!"...right?) LOL.

Ok, that wraps up the comedy portion of my act. Moving on to the business at hand...

The photo shows the existing wet vented 1-1/2’ bathtub drain. The blue “X” marks the location for the new shower drain. The 1-1/2” vent pipe goes straight up through the roof. The “drain” pipe is 2”.

My question is how best to plumb the shower drain. I know the shower drain and trap needs to be 2” but I’m not sure where exactly it needs to, or should, enter the horizontal 2”drain. Does the fact that it’s a wet vent dictate where it enters the drain? Does it need to enter via a san-T in the same exact location that the existing 1-1/2” tub drain currently does (but replacing the 1-1/2” san-T with a 2” san-T and using a longer trap arm to reach the shower drain p-trap (see diagram)?

Alternatively, can the existing san-T and tub drain be eliminated entirely and have the shower trap enter the drain a little farther down (after the shower drain rather before) or is that not possible due to the venting issues or would entering farther down create problems with obtaining the right degree of slope between the vent, trap weir and drain? This approach would turn a section of that 2" drain pipe into a horizontal vent though and I don't think that's allowed.

Did I explain it so that you understood what I was describing? I have a tendency to over explain and use 3 sentences when one will do and sometimes that just makes it more confusing so please let me know if that is the case and I will try to make it clearer. Also, if you have any questions about anything please ask. I’ll be monitoring the forum so I’ll be able to respond quickly.

I would greatly appreciate your help and advice as well as any comments or suggestions you may have.

Cherrie

 

[James Henry]

I couldn't get all the way through your book but it did make me laugh when you said you use three sentences when you could have used just one.

 

[Sponsor]

 

[wwhitney]

In the spirit of the OP, I will perhaps also use 3 sentences when 1 sentence would do:

I'm unclear on whether a manufactured home has to comply with the state's plumbing code (the UPC for WA state), or whether there's a national code that applies. The latter would make sense to me regulatorily, but I don't know. If there is, and if it's based on the IPC, then you have a lot more flexibility, assuming that it still applies to your remodeling and not just to the original work done in the factory.

So I'm going to make my comments based on the UPC, and will note where the IPC differs. You'll need to figure out which code applies to your current work.

Your tub was not wet vented, it was dry vented. The vent path was from the san-tee up the 1-1/2" vent, which should not be carrying any drainage, so that's a dry vent.

Your lav is dry vented by an AAV. That's not allowed under the UPC (IPC allows an AAV, but the AAV needs to be accessible for maintenance, such as under the lav or in a ventilated wall box.). So for UPC compliance you'd need to replace the AAV with a dry vent that goes up through the roof, or connects to the tub dry vent at least 6" above the lav flood rim.

Your WC is wet vented, as its vent path is upstream from the combo through the lav drain to the lav's vent. Since there is drainage through the WC's vent path, it's a wet vent. Except it looks like the lav drain is 1-1/2", and the UPC requires a 2" vent (wet or dry) for a WC, so it should be upsized all the way to the roof (the existing 1-1/2" vent is sufficient under the IPC).

Now, as to the shower, if you are able to change the san-tee to 2x1-1/2x2, and keep it in its current location and orientation, and bring the shower trap to the new 2" side inlet with proper slope, that will work fine under the UPC. (IPC allows a 1-1/2" drain for a shower of up to 5.7 gpm, which means you might be able to keep the existing 1-1/2" drain.)

However, you may have an issue as it appears part of the vent is both outside the wall and above the subfloor, so it would be poking out into your shower space. (You could give up a little shower space and fir the wall or add a bench or elevate the shower pan to enclose it.) Your pencil drawing looks like you have tilted the san-tee to an angle that is more than 45 degrees off plumb--that would count as horizontal and would not be allowed. The san-tee has to be vertical, which includes the orientation in your picture, but no shallower of an angle.

If you can't get something like the current arrangement to work for a dry vent, then if there's a solid wall between the shower and WC that the shower drain passes under, you could move the vent takeoff to be under that wall. You'd use an upright combo for a vertical vent takeoff. (IPC would allow a san-tee on its back, but really the only reason to take advantage of that allowance is if you are space constrained).

Your other option for venting the shower is a horizontal wet vent. Which I will postpone discussion of, as this post is already too long.

Cheers, Wayne

 

[Cherrie]

Hello again. Wayne. You are becoming my savior in all things remodel.

I had a family emergency and wasn't able to respond until now so I apologize for the delay. Getting this right is very important to me and I am beyond grateful for your help. With that said I am going to address your comments in the order you wrote them (and I will do my best not stay on point and not babble needlessly (starting now).

All manufactured homes follow the "Federal Manufactured Home Construction and Safety Standards" set by HUD. The codes apply to both original construction as well as all remodeling and alterations. I'm sure they must share some of the same standards as the UPC and the IPC but they are significantly less restrictive than both of them.I guess it depends on how you look at it but I'd say that's good news for me (yippee!)

Ahh, dang it!!! Most of this response just now disappeared when I went to post it. The system logged me out and when I logged back in everything I wrote from this point forward was gone. I'm too tired and my head hurts from eye strain to even attempt to redo it. I'll come back to it in the morning, ok?

Thanks,
Cherrie

 

[James Henry]

who cares if the toilet flange is centered 15 inches from wall, right?

If the toilet is centered 15" from the SIDE of the toilet to the wall that is code.

 

[James Henry]

As long as you have at least one vent on your plumbing system in the home going through the roof this should work. If this will pass inspection I would ask if it is OK to cap the bottom and top of the abandoned vent going through roof.

 

[wwhitney]

I'm guessing the tub vent may be the one vent going through the roof, as I see no other reason it was originally installed.

Cheers, Wayne

 

[James Henry]

I'm guessing the tub vent may be the one vent going through the roof, as I see no other reason it was originally installed.

Cheers, Wayne

The kitchen sink most likely has one.

 

[Reach4]

because hey, who cares if the toilet flange is centered 15 inches from wall, right?

Seems to match IPC and UPC on that point.

https://www.govinfo.gov/content/pkg...2019-title24-vol5-part3280.xml#seqnum3280.111

§ 3280.111Toilet compartments.Each toilet compartment must have a minimum width of 30 inches, with a minimum clear space of 21 inches in front of each toilet. A toilet located adjacent to a wall must have the center-line of the toilet located a minimum of 15 inches from the wall. A toilet located adjacent to a tub must have the center-line of the toilet located a minimum of 12 inches from the outside edge of the tub.[78 FR 73981, Dec. 9, 2013]​

In IPC it is 405.3.1 and UPC 307.1. https://shop.iccsafe.org/media/wysiwyg/material/8950P235-sample.pdf

 

[Cherrie]

The kitchen sink most likely has one.

Nope. Kitchen sink has an AAV.

 

[Cherrie]

If the toilet is centered 15" from the SIDE of the toilet to the wall that is code.

Sorry, it didn't even occur to me that the reference to 15" might be interpreted that way. I am aware that it meets code for distance from the sides of the toilet . I actually was referring to the distance between the center of the flange and the back wall. I realize it's not a code violation or anything like that, it's just one of those things that result from poor planning and lack of attention to detail that annoy the you-know-what out of me because it could have easily been avoided but instead it sticks out like a sore thumb (and I was being sarcastic).

 

[wwhitney]

Nope. Kitchen sink has an AAV.

Then if the tub is the only vent through the roof, you can't eliminate that roof penetration. But you could change the lav vent to be an atmospheric vent, connecting back up to the current roof penetration. And then possibly wet vent the new shower, avoiding the need for a vent connection there. If that option is of interest, we can get into wet venting.

Cheers, Wayne