bathroom drain/vent ~ advise sought, is studor a bad path?

[muldoon]

I am now getting ready to put in a very meager bathroom and would like some advice.   Quick point, no building codes, unincorporated area, no permitting.  I want to do it correct because I do not want any problems with it, but I also do not need to overbuild for a bathroom that might see 1 weekend a months use 9 months out of the year. 

4x4 upright shower, toilet, sink, basically lined up next to each other on a 12' wall.  On the other side of that wall a single kitchen type sink roughly where the sink is on the other side.  All the water plumbing would be within a 10' span. 

In the middle of that section is the toilet, the toilet would sit directly in front of the main drain/vent stack and connect to the drain pipe.  The drain being a 4" that goes to septic away from cabin, and extends up like a vent stack would in the wall. 

For shower, under floor drain with trap, coming back to a main 4" drain. 
Next the toilet goes into the drain. 
above that drain have the two 1.5" drains for the two sinks.

Those should be all the drain lines egressing to the septic.  For venting,

Above all of those, have first the shower come back into the main vent, then the sinks.  Something like a christmas tree effect. 

All fixtures have a path for water, and a path for air going back into the same main drain stack well above the highest water drain.

...
(for a cleaner visualization, rather similar Pa_kettles video in this post:  http://countryplans.com/smf/index.php?topic=3409.0 )
The difference being vent drains included for the two sink outlets - matching the red aux vent for the shower so to speak. 


Now for the meat of my question, can I avoid doing a roof penetration with Studor type vents with this minimal of a usage?  Actually I likely would finish the top of the main vent/drain with a tee, then put one of these vents on each end.  (Since it is mechanical, two is better than one I am thinking).  They will be semi-accessible in the overhead space over the bathroom.  a panel style access area that will also hold a bosch 6 gallon hot water heater. 

I dont want to penetrate the roof.  I don't want to mess with flashing and sealing that will leak eventually anyway.  I want to be lazy and do it the easy way using the 1 way valves..  Plenty of places on the internet seem to indicate this is acceptable.  Plenty of places seem to indicate it is not. 

Any thoughts on this plan? 

[Redoverfarm]

I am sure there are others on this board that might give the same/different advice but if at all possible use a vent stack through the roof or at least into the eve/soffit area.  There is places for a studor valve but I would not want to depend on it solely for the vent.  When there is a single appliance that is by itself I would consider and have used in this circumstance.  They have to be in an area to draw air to operate properly.  Wall cavities are not the best because they can draw no air.  Depending on the type roof you are using they make good vent boots both for shingle ande metal roofs that have proved to be leak proof when installed correctly.  I think I would reconsider with the exception of the lone appliance. Just my $.02 worth.

[muldoon]

Thank you for the reply.  

Just pointing out, it would not be in a wall cavity.  It would be above the bathroom ceiling (8') but under the gambrel ceiling of the interior.  Think of the space over that bathroom plan being semi-loft style where it can be accessed via a panel.  Inside that dead space would be a water filter, a water heater, the raised ventstack, and a gfci outlet.  

I do not think side or soffit will work, it is a gambrel design with 6' sidewalls.  The gable end is a possibility except that will be the primary entrance and I dont really want to vent right "at the front door" so to speak.  

As for the point regarding single device, would I be daft to say... what about 3 studor vents instead of 1? 

[bayview]

   Studor vents are air admittance valves.   Septic/Sewer gases need to escape.   I don't see any way out except to penetrate the roof . . .

/.

[muldoon]

Bayview, that certainly seems to be the crux of what I am asking. 

If gasses do need to escape then I agree with your logic and see no alternative.  However, if air pressure just needs to be regulated so that traps are not drained, and really air only needs to come in but not out, then I see no reason why it would not work.  I have read both sides of this and it seems there are logical cases for both.  There is a big industry for these AAV devices and they are allowed in many places and in use all over.  Some with success, some not. 

I guess I am just trying to understand the incongruity here.  Thanks again. 

[ScottA]

You need at least one vent through the roof. It's best if all fixtures are vented. You can tie them all back together above the highest fixture if you want. All drains must enter the main drain above the toilet connection to the main if you are using only 1 vent for more than one fixture. They make special tees that have extra inlets on the side(s) for just this purpose. If the other fixtures have their own vents then it doesn't matter.

[MountainDon]

C'mon, not all roof penetrations leak. Before we re-roofed I gave the underside of the then 22 year old shingled roof a thorough inspection. No traces of any water issues anywhere. You only have to do it once if it's done right.

[muldoon]

I think I have enough consensus that my question has been answered on venting and the roof penetration itself. 

Thank you guys for helping me get back on track and answering my questions.  It is good to get this stuff sorted out in the planning stages. 

[Alan Gage]

Been doing a lot of studying on plumbing the last few months trying to get this same stuff straight in my head. I had the same thought as you originally, just use AAVs and skip the roof vents. But the reason at least one roof penetration is code is so that air in the vent line can be exhausted as well. Say you drain the sink or tub and a slug of water fills the whole line. That means it's pushing air ahead of it which can push up past the traps in other fixtures if it's not allowed to exhaust through the roof.

My place will be a full time residence but with only one bath so not real high demand. I'm going to use an AAV for the kitchen sink and a 3" vent through the roof where the toilet enters the line. Downstream of the toilet will be the bathroom sink and clothes washer. Upstream will be the kitchen sink and shower.

2" line buried under the slab for the kitchen sink and shower and 3" downstream of the toilet. No codes enforced here but code says nothing smaller than 2" buried under a slab. Sounded like a good idea. With the larger than necessary pipe diameter I could probably get by fine without any vent for the kitchen sink but I'll do the AAV anyway.

Alan

[Canvasman]

I can speak only for Wisconsin codes. The vent in my house currently under construction, exits thru the gable end wall, no roof penetration as I wanted nothing thru roof, to possibly leak.
Eric

[Okie_Bob]

I built a garage with one end enclosed as an apartment with a bath and small kitchen to use while building my house. Finished garage about 7 or 8 years ago and finished house about 3 years ago. I have a metal roof on both structures and didn't want any penetrations on either. So, I used studor valves in both and to date have no problems with either application. I do live in a location that has no inspections or permits required and I'm not sure if this would meet any code requirement in other areas. I'm very pleased with the metal roof and the fact there are no penetrations in it for anything. Studor valves have performed flawlessly to date but, of course they could fail tomorrow since I'm bragging on them!
One last thought, they both are located in an attic where they have full access to air but, the attics are also enclosed with Icynene sprayed insulation for a pretty airtight application.

[bayview]

I built a garage with one end enclosed as an apartment with a bath and small kitchen to use while building my house. Finished garage about 7 or 8 years ago and finished house about 3 years ago. I have a metal roof on both structures and didn't want any penetrations on either. So, I used studor valves in both and to date have no problems with either application. I do live in a location that has no inspections or permits required and I'm not sure if this would meet any code requirement in other areas. I'm very pleased with the metal roof and the fact there are no penetrations in it for anything. Studor valves have performed flawlessly to date but, of course they could fail tomorrow since I'm bragging on them!
One last thought, they both are located in an attic where they have full access to air but, the attics are also enclosed with Icynene sprayed insulation for a pretty airtight application.

   How do you vent septic/sewer?

/.

[UK4X4]

Rather than start a seperate thread - I too have questions regarding the vent stack-

I'm not so worried about water ingress but snow buildup ! - I don't have a loft - so I was looking at exiting the wall on the ridge support side

or I'm on the lowest corner of a 90#/ft sloped roof is this OK by code ?  two off 45deg and the pipe is outside the roof line.

if not the pipe will be at the lowest part of the roof on both sides of the house.