Wet / Dry Vent Under-slab Questions - long time listener, first time caller

[GizmoBuilder]

Hello Terry Love forum,

I have come here many times over the years lurking and reading for my DIY reno projects. I am NOT a plumber, full disclosure. I am an electrical nerd (yes one of those engineery types). Due to unforeseen and complicated circumstances I designed my own house and trying to build it and lack appropriate funds to sub everything out. The drain system for the plumbing was one such thing is was PLANNING to sub out but out where I am it is almost impossible to find someone to do work. I found one guy but he isn't licensed and the terms are not really good for my situation. So I am doing this part myself.

Important points:
1. I have CMU up and waiting to pour the floor until I can get this under slab plumbing done so I need to do it asap

2. I have a 3" drain under my footer going to a septic tank which will have a pump to pump it up to the main septic tank (the upper levels of the house will gravity drain into the main tank. Right now I am only concerned with the basement because I plan to live in it while building the rest of the house because I am tired of being homeless.

3. There are NO codes where I am, meaning there are no codes, no inspections etc.... yes these places still exist. That said, I do want this done correctly. I overbuilt my walls and footer despite there being no codes. I don't need to overbuild the plumbing system however but lack of codes doesn't mean I want lack of quality.

I have attached a 3d floor plan which shows the bathroom group and on the other side of the wall is a laundry and sink

I have also attached some terrible renderings (because me building plumbing models in SketchUp is time consuming and way more difficult than it appears) that show the proposed layout. I think you get the idea. Ignore the perspective 2d/3d I was annoyed trying to draw this without speding 100 hours on it, proving I am also a bad hack architect.
The toilet will have a low heel inlet 90 at the top right under the wall (that wall isn't load bearing so I will just position the heel for the vent under the wall).
The other bath fixtures will tie into the 3" main line with WYE 45's (2" drains) wet venting from the toilet vent
The laundry and laundry sink will have their own vent which will tie into the toilet vent somewhere above in the joist space before heading up a chase that I have planned for the drain/vent through the floors

How terrible is this plan?

 

[GizmoBuilder]

So I don't have room under the slab for the toilet to have a vent off of the top like I drew it.
I have reconfigured this so the toilet wet-vents through the lav or bath.
The bath has it's own dry-vent (shown in that wall section and then the trap / trap arm will go out to the rough-in area under the tub)
The washer/laundry sink will connect on it's own.

Notes:
main line is 3"
lines connecting to main line from lav, bath, washer is all 2"
shower, lav, washer/sink will all connect through individual 3"x2 Wye fittings
Vents coming off from lav, bath, washer 1 1/2" connecting together in the joist space above.

I think this is okay. Can someone please critique me?

 

[Sponsor]

 

[GizmoBuilder]

So I don't have room under the slab for the toilet to have a vent off of the top like I drew it.
I have reconfigured this so the toilet wet-vents through the lav or bath.
The bath has it's own dry-vent (shown in that wall section and then the trap / trap arm will go out to the rough-in area under the tub)
The washer/laundry sink will connect on it's own.

Notes:
main line is 3"
lines connecting to main line from lav, bath, washer is all 2"
shower, lav, washer/sink will all connect through individual 3"x2 Wye fittings
Vents coming off from lav, bath, washer 1 1/2" connecting together in the joist space above.

I think this is okay. Can someone please critique me?

Buehler..... Buehler... anyone?
I could really use some advice, planning to do my rough-in on Friday, please.

 

[GizmoBuilder]

@wwhitney I see you are an expert in this realm on the forum. Could you please give your opinion for my sanity check?

 

[wwhitney]

@wwhitney I see you are an expert in this realm on the forum. Could you please give your opinion for my sanity check?

Not following the meaning of the zig-zag shown at each of the traps, using 4 different quarter bends. A trap has only the equivalent of 3 (one u-bend, one quarter bend).

Anyway, starting at the WC, I see the order of other drains connecting to its 3" line is currently bathtub, lav, and laundry+laundry sink. An order easier to vent would be lav, bathtub, and laundry+laundry sink. For that order, you would need a dry vent takeoff for the lav (at the lav trap elevation), and 1 or 2 dry vents for the laundry and laundry sink. With the tub in between the WC and lav, the tub or the WC needs its own dry vent.

With the laundry and laundry sink joining downstream of all the bathroom fixtures, venting for the bathroom and venting for the laundry are separate issues. The laundry can be vented with one dry vent in two different ways: option 1, the IPC allows a single trap to be shared by the standpipe and the laundry sink, at the sink outlet, you use a quarter bend to a horizontal drain to a san-tee installed in the standpipe, above the standpipe trap. Then the trap outlet goes to san-tee with the dry vent taken off the top and the drain outlet at the bottom. As always with venting separate traps (non-WCs), the drain's total fall between the trap outlet and the vent connection is limited to one trap diameter.

Option 2 would use two traps, each connected to a san-tee, which are stacked on top of each other, with the dry vent taken off from the upper san-tee. The pipe between the san-tees is the drain for the upper fixture, as well as the vent for the lower fixture (which is the definition of a wet vent). Pretty sure that's all fine in 2" (1-1/2" for the laundry sink trap arm) if the laundry sink san-tee is above the standpipe san-tee; would have to double check if you want the opposite order.

As to the bathroom group, the lav needs a dry vent takeoff in the wall behind it (because the takeoff has to be within 1-1/4" or 1-1/2" in elevation from the trap outlet, depending on whether the trap size is 1-1/4" or 1-1/2"). Then that lav drain can horizontally wet vent both the WC and the tub. The lav drain has to join either the WC or tub first, and then the combined drain can join the other fixture's drain. The tub trap arm is from the trap outlet to the horizontal wye where it joins the lav or lav+WC, and as usual is limited to one trap diameter of total fall.

Cheers, Wayne

 

[GizmoBuilder]

@wwhitney , you sir are a gentleman and a scholar! Thank you for the reply. If you are ever in TN or the next time I am in N. Cal I owe you a beer or steak or both maybe!

Regarding,
"Not following the meaning of the zig-zag shown at each of the traps, using 4 different quarter bends. A trap has only the equivalent of 3 (one u-bend, one quarter bend)."

Ignore my terrible drawings please the first set of drawings was dumb on my part and even made an S trap which I know is no bueno.


Regarding,
"Anyway, starting at the WC, I see the order of other drains connecting to its 3" line is currently bathtub, lav, and laundry+laundry sink. An order easier to vent would be lav, bathtub, and laundry+laundry sink."

The reason I had it arranged like this is because of the angle entry into the 45 on the WYE is more favorable. I don't want to mess with using a double WYE so instead was going to use WYE then WYE to make the connections easier. And putting the Lav just a little further downstream gets me into it closer to 45 (i might still need a 22.5 on either this and/or the tub to get it together).

That said, my intent was to have a dry vent for both the Lav and Tub (the tub vent goes through that bulkhead wall there which actually lines up with a elec/plumb chase from upstairs and then the trap arm extends under that wall to the trap what is shown in the picture where the pipe is located is the vent (the crete block is (so concrete doesn't get poured there so I can adjust the inlets after setting the walls) where the tub gets connected). I was going to tie the vents together in that space and go up through the roof. I made a new drawing that probably explains it better. Does this work?

For me the crux of the issue is what I read is the toilet needs to be the last fixture and downstream of others (except 1?) on a wet vent system. But I don't understand why what I have will not work. It effectively has 2x wet vents through the Lav and Tub and besides doesn't the toilet siphon itself anyway? I cannot put a dry vent for the toilet because of running a vent horizontal under the slab. The only other option I can think of is to have a low-heel turned down at the toilet and the Lav or Bath entering there but that arrangement seems to be a. not allowed, b. a generally bad idea. So that is the confusion for me.
So does this work? It seems like it should to me.

Regarding Laundry,
Yes thanks for your comments I was planning for option 1. I am treating the laundry and sink as a totally separate group with its own vent. The biggest thing is I am just running 1x 2" down under the slab for both which works okay based on your comments and what I read before.

Hopefully this makes more sense?

Thank you and very truly so!

 

[wwhitney]

That said, my intent was to have a dry vent for both the Lav and Tub

You can do that if you prefer. I didn't follow your description of the vent routing. But I meant to say that any two vents can join at an elevation that is 6" or more above the fixture flood rims of all the fixtures served.

For me the crux of the issue is what I read is the toilet needs to be the last fixture and downstream of others (except 1?) on a wet vent system.

First point: this applies only to the UPC, and TN uses the IPC. So it's a non-issue for you. Second point, because you are dry venting the tub, your layout satisfies this restriction anyway. The WC is being wet vented by the tub, and that is the only wet vented fixture. So the WC is the last fixture on the wet vent.

BTW, for the UPC (which does not apply to use), the dry vent on the tub would need to be 2" because it is venting a WC. Your dry vents can all be 1-1/2".

Cheers, Wayne