DWV Plumbing Diagram Critique for Small House

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Zane Bridgers

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Hello Terry and co. and many thanks for the wealth of information you have provided to the public! This has been an excellent resource thus far - not sure where I'd be without it!

My girlfriend and I are building a 720 sq ft. house in Northern New Mexico, Climate Zone 5a, UPC 2012. It will be a monolithic slab on grade, so it's in our best interest to get this right before the concrete starts pouring.

Just looking for a general red flags here - that is a 3" Sewer Line FYI. I still have to take the home owners exam but have been studying.

Plumbing-Diagram.jpg
 

Terry

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If the lav is run with 2" it can vent the shower assuming the shower is wyed off of the lav line. This would also vent the toilet.
The washer gets it's own vent, as does the kitchen sink.

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Zane Bridgers

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Ah that's awesome! Makes sense... Thank you so much Terry! You're the man! Here is another quick diagram to make sure I am understanding correctly.

A couple other questions came up when trying to draw a single line elevation: Is it best practice to drop drain lines vertically after the p-trap to get below the slab vs. 45* as I drew (diagram right - kitchen sink)? Does the sewer line need to exit the building below the frost line (36" here) in the 2012 UPC? I've read elsewhere 1" EPS foam is equivalent to 12" trench depth - could foam substitute for some of that depth?

It seems like compounding expense and complication since the septic tank / leech field also then needs to be that much deeper.
IMG_7250.jpg
 

Zane Bridgers

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Hi Terry -

Any chance you could comment on my single line elevations? These are what the mechanical department uses to issue a permit, so I want to make sure nothing is way out of line! I think this is what you were getting at with the 2" wet vent for W.C., Shower & Lav...

Many many thanks!
 

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Zane Bridgers

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Sorry to dig up an old thread - I got stamped plans back and don't totally understand why the inspector added two VTR's. I thought maybe wet venting was prohibited in the state, so I got all the fittings to do away with the wet vents, but then just confirmed this morning that it is permitted as per the 2015 UPC.

Here are the plans with markup from the inspector:

plumbing-plans.jpg


Here's the assembly without wet venting, which frankly seems pretty ridiculous. Without disregarding the feedback from the inspector, what would be a simpler approach to adding a vent for the WC and shower? The only constraint is I only have 10" vertically to keep the drains under the slab and still have proper slope.

plumbing-no-wet.jpg
 
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Reach4

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VTR is vented through roof, I think.
 

Zane Bridgers

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Yes, it is, but I called to confirm it just means they want vents from those trap arms. It seems pretty ridiculous to have 3 VTR's within 5 feet of each other. I'm looking for the simplest way to tie the W.C vent, shower vent, and lav+shower drains into the sewer+stack. The main issue I'm having is that a 3" Combo Wye is already 12" when set vertical, and I only have 10" or so, so everything has to be at 45* coming out of the sewer.

Can a santee's be used for drains at 45*?
 
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Terry

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Santee are used on the vertical.
Wyes and combos on the horizontal for venting and for incoming branches.
I see he added a cleanout for the washer, that's good. He wants a vent for the shower that revents at 42". He's not allowing the lav to wet vent the shower. I don't know why.
 

Zane Bridgers

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Right... I can't seem to find anything specific in the UPC prohibiting it. Does Table 1002.2 (2012 UPC) imply that all trap arms must terminate at a vent of some sort? i.e. it is not permitted to have the lav drain into the shower and then hit a vent, even if it is within the prescribed 60 inches?

I noticed in 908.2 that horizontal wet vents are only allowed to have one fixture upstream. I'm afraid that makes using the main sewer as a wet vent for the shower difficult, since the lav and WC are upstream.
 

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Right... I can't seem to find anything specific in the UPC prohibiting it. Does Table 1002.2 (2012 UPC) imply that all trap arms must terminate at a vent of some sort? i.e. it is not permitted to have the lav drain into the shower and then hit a vent, even if it is within the prescribed 60 inches?

I noticed in 908.2 that horizontal wet vents are only allowed to have one fixture upstream. I'm afraid that makes using the main sewer as a wet vent for the shower difficult, since the lav and WC are upstream.

The lav can be upstream, but not the toilet.
 

Zane Bridgers

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Hmmm ok. Does this make sense then? I originally drew it with the lav hitting the shower trap arm and then the double santee, but this way there is some redundancy since the toilet techically has a 2" wet vent from the lav and then a 3" vent at the double santee, both within 60" of the W.C. I have a bit more vertical clearance than I originally thought.

IMG_7459.jpg
 

Zane Bridgers

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Thanks Terry! Is that because of snaking? Would you stack two santees? I can't seem to find any but would a 3x2x2 double fixture work as well? The issue with the stacked santees + 3" combo is the stack is almost 20" tall. Some kind of offset double santee would be great if it existed...

IMG_7461.JPG


Any issues with draining the laundry directly into the main stack like this?

IMG_7460.JPG
 

Terry

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The washer can't wet vent the shower. That needs it's own vent, which it has, and the shower needs a vent, which can't be the washer at all.
The kitchen sink gets a vent the washer gets a vent.
The shower can only use the toilet vent, if it's not shared. If you bring in the washer and the sink downstream, problem solved.
 

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That works. If you have an issue with height, you could also throw a wye in there a bit further downstream and bring it over to the washer and sink.
 

Zane Bridgers

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Ok that sounds like a plan! Thanks so much Terry and Reach4. You have been a huge help! I will post up some photos when it's roughed in and inspected.

Bizarrely, I had texted the previous image to our inspector and he said it was "code compliant as per section 908.2 of the 2012 UPC." Is it possible this is a regional thing? That drawing has both the double santee and laundry draining above, so it seems like a double no-no, but he didn't mention either. Maybe because it's 3"? Is there a section of the UPC I can reference for that violation, or is it in the regional administrative codes?

I'm planning to rough in that 2" wye for the laundry because once the slab is in there's no going back. I'll either use it, cap it or make it a cleanout, but at least the option is always there.
 
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