# Self Sufficiency/Living off the Land or Off the Grid > General Homesteading >  PLUMBING Roof VENTS for a simple cabin.......Is one vent enough.....?

## Sourdough

If all of the plumbing is Back-to-Back in the same interior wall, can you get by with only one roof vent for one toilet, one shower, two sinks......?

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## Rick

I don't know why not. I've never plumbed more than one drain-waste-vent and I've never had any problems as long as all drains are tied into it. What are your concerns? 

WE can probably help with this one, too.

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## welderguy

Ive seen a lot of A-frame houses and a lot of mobile homes only have one plumbing vent, Im guessing a lot will depend on building codes in your area.

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## Pal334

One is completely adequate,especially since you are "back to backing" it what I have done though is make it slightly oversize. No real reason, just figure the bigger the better

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## Sourdough

> What are your concerns?



DEATH, caused by (Colorless & Odorless) Methane Gas. or systems not draining because of air-lock.

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## Rick

Okay. I thought you had some specific concern since you're on a septic. You have to have air backflow to feed the aerobic bacteria as I understand it. I've never been on septic that's why I asked if you had a concern.

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## Sourdough

As I understand it the MAIN reason for roof vents, is so the second floor dump from a bath-tub or toilet does not back-up into a first floor sink/shower/etc.

The problem is it will be snowing in about 80 days, so I need to think ahead about drilling 3" holes in the roof.

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## crashdive123

> If all of the plumbing is Back-to-Back in the same interior wall, can you get by with only one roof vent for one toilet, one shower, two sinks......?


Yes..........

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## Sourdough

Thank you, everyone. And so it shall be one 3" roof vent. (I like them apples)

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## Rick

Here's some reading for you.

http://en.wikipedia.org/wiki/Drain-waste-vent_system

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## Pal334

> Thank you, everyone. And so it shall be one 3" roof vent. (I like them apples)


Since we handled that one well, shall we take on world peace or something next?  :Smile:

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## Sourdough

> Since we handled that one well, shall we take on world peace or something next?


That or: UNDERSTANDING WOMEN 101

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## Rick

Hot dang! Now we're talkin'. The difficult we solve right now. The impossible takes a while longer.

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## wareagle69

is this all on one floor? for the fixtures mentioned 2 in vent is more than adequate,until you go thru the roof (vtr) then cut a peice of 3in about 18 inches long and stub it thru the roof at least 6" about the roof depending how high up you are venting out. the reason for the 3" is just for frost hoar, 3" should not frost closed preventing venting. imagine sticking a straw in a soda then putting your finger over it, fluid stays in the realese your finger fluid go out-venting. Same as poring out that 2ltr bottle of soda glug glu glu, now pucnh a hole in the bottom , and vola smooth drainage-venting.
now if one sink is downsatirs then the vent needs to run upstairs and tie into the vented fixtues above the flood level rim of you highest fixture-normally the sink and questions SD  give me a call and i'll walk ya thru it

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## kyratshooter

You need to place the stack within 5-6 feet of the drains.

If you have all of them back to back you should be able to accomplish that.

My kitchen sink is 10' fron the stack and it girgles some.  I knew better when I did it.

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## Pal334

> That or: UNDERSTANDING WOMEN 101


Oh yea!!!!  I am your man for that!!!  It has only taken me a bit over 35 or 40 years (mmm memory may be part of my problem also) to realize there ain't no such thing . And I have the bruises to prove it

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## Sourdough

> is this all on one floor? for the fixtures mentioned 2 in vent is more than adequate,until you go thru the roof (vtr) then cut a peice of 3in about 18 inches long and stub it thru the roof at least 6" about the roof depending how high up you are venting out. the reason for the 3" is just for frost hoar, 3" should not frost closed preventing venting. imagine sticking a straw in a soda then putting your finger over it, fluid stays in the realese your finger fluid go out-venting. Same as poring out that 2ltr bottle of soda glug glu glu, now pucnh a hole in the bottom , and vola smooth drainage-venting.
> now if one sink is downsatirs then the vent needs to run upstairs and tie into the vented fixtues above the flood level rim of you highest fixture-normally the sink and questions SD  give me a call and i'll walk ya thru it




Wareagle, Everything is on one floor, still a 11' by 23' one room cabin. Two Questions: first, I get a lot of snow, often 6' to 10' of snow on the roof, does the 3" vent need to extend higher above the roof........? 

And I am wondering why I can't run it through the ceiling into the well ventilated 4/12 pitch roof truss system, and with a "T" and double vent it out the gable ends, as this area is protected by roof overhang, and eliminates the deep snow problem, as well as the damage to the vent when shoveling snow off the roof.

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## crashdive123

I know you said it is well ventilated, just remember some of what vents is flammable.

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## randyt

I would vent it out the gable end and glue a 90 degree ell on the end with the 90 pointing down and put a screen on the 90 to keep birds out of it. this method is now approved by  international plumbing code. I do it this way now and then but prefer to go through the roof out of habit.

if you feel you need more vent you can also revent your fixtures. which is basically a vent that ties into the vent in the attic but you still only have one penetration. also I try to tie a fixture like a sink into a vent, I feel this is a good practice because it keeps the base of the vent stack washed.

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## Alaskan Survivalist

It is far simpler than you guys make it out to be. The vent is simply to give the fluids someplace to go. Fluids going into a pipe must displace whatever is in the pipe, even air. It is the opposite of a gas can that needs to be vented to get gas out of it. You only need one vent at the end of the system so the air in the pipe can be pushed out of the way for the water. Your septic system should have another vent in the pipe ten feet from the house, two in the tank and one in your pit.

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## Ole WV Coot

I got lost in complications. I have a bath, shower, sink & commode plus backed up to the kitchen sink & dishwasher. This is on a 3" vent. The curved traps are there to hold water and block gas. The commode should be very close to the main stack, check codes or online. The vent is for air pressure not just let gas escape. Without it the commode won't flush, drains won't drain etc. I have another 3" from the basement to the roof simply because the bath is located far from the one upstairs and I have a small kitchen downstairs, but you can extend the pipe as far as you want above the roof. Mine are 16" on the 4-12 pitch of the metal roof even tho I don't need to worry about that much snow. I put in a water saver commode that uses 1 1/2 gal of water and it works great on a septic system. A 2" would work, but a 3" isn't overkill and works better as a vent. I took mine up inside a non support wall straight up cutting a hole in the 2X4, got to the attic, dropped a plumb line to the center of the pipe, drilled a hole in the roof, got on the roof, pushed the pipe in the enlarged hole, used a regular boot, extra sealant and a screw every inch around the flange for more overkill. The real point of all this is keep the commode very close to the main stack, need at least 12" from the wall to center, don't forget traps on everything else and remember water in the traps block gas.
I even ran 20' of radiator hose from the dishwasher to the garbage disposal just because the wife wanted it in a certain place and it works great, just drilled the backs of cabinets and zip tied it in place. Just get the vent above the roof.

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## your_comforting_company

> And I am wondering why I can't run it through the ceiling into the well ventilated 4/12 pitch roof truss system, and with a "T" and double vent it out the gable ends, as this area is protected by roof overhang, and eliminates the deep snow problem, as well as the damage to the vent when shoveling snow off the roof.


As a fella who has to fix leaking roofs on a regular basis, I would suggest this method rather than cutting a hole in the roof. Most of the new construction houses are using attic venting rather than roof venting for that very reason. We don't get snow here, but any time you put a hole in your roof, you are asking for trouble. 
IMO, as a roofer, I say vent it to the gable and don't make a hole in the roof. You might want to add a fan at the gable to increase draw through the attic or make a hole in the gable vent that will vent the pipe outside under the eave.
City sewer systems in town have different regulations, so you might want to check the building codes just to be sure. In town, a 4" pipe is required.
A roof with no holes is much less likely to leak than one with 1/8" thick rubber boots that will rot in 5 years and need replacing. If you MUST vent through the roof, use the lead boots and curl the flange edges so that water cannot run sideways off the boot and under the shingles.

Do NOT put holes in the bottom exposed edge of the boot flange if you go that route. ANYWHERE on a roof that a nail head is showing WILL LEAK EVENTUALLY. NEVER EVER PUT A NAIL WHERE THE HEAD WILL BE EXPOSED!! Even the metal roofing screws with the rubber washer will rot in 5 or 6 years (I've had to change every screw in several metal roofs and I will not ever endorse metal roofing under any circumstance because the screw will leak in a few years and most of them will need replaced!)

If leaks are your main concern (as they are for me), don't make holes in the roof!!

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## NightShade

Sourdough... I am a licensed plumber.... 1 vent is fine.. I don't even hafta open my fixture charts for this one... Back to back kitchen / bath 1 vent. Thru roof is fine.. As you said.. 3"... You need 3" because if you only have 1 vent it must be full sized to properly operate toilet...

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## randyt

the house I grew up in when I was a kid didn't have any vent. I don't remember any problems except during the spring thaw, at that time we used a outhouse. now all these years later being a licensed master plumber I see all kinds of different situations.

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## Winnie

I don't think there are many plumbers in the middle of Alaska KM :Blushing:

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## crashdive123

> I don't think there are many plumbers in the middle of Alaska KM


I removed his post where he was recommending a plumber.  Interestingly (not really) his link that said "on-line" plumber had nothing to do with plumbing.  I guess the spammers out of the Philippines get confused from time to time.

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## Winnie

Oh :Blushing:

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## Sourdough

> Thru roof is fine.. As you said.. 3"... You need 3" because if you only have 1 vent it must be full sized to properly operate toilet...



NightShade, I am VERY strongly leaning towards NOT running it through the roof, but into the trusses, and then install a tee and vent it out both gable ends, do you see any problem with this system.........?

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## NightShade

Not really.. Though condensation may build up and freeze in the eves during cold months...that's not legal to do in Mass. But I know in other parts of the country it is accaptable.you can probably find local plumbing code online... I know the mass plumbing code is online..

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## NightShade

If you do decide to go thru roof....
You can extend vent higher than 2 ft... If u do though you wanna increase vent thru roof 1 pipe size (4")
If you don't increase the pipe size and go higher than 2 ft condensation will freeze in pipe and eventually totally block pipe in colder temps.. Thus you would have no vent... 
If u do it that way there will be less fittings and pipe to buy therefore saving sum money.

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## Sourdough

Thanks...........

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## Sourdough

Thanks Again, and one more related question: Reference framing of the wet (Plumbing) wall, I know it needs to be 2"X6" studs, so as to allow for the 3" vent pipe. Other than 2X6 is there anything else special about this wall.......? 
I assume it can be 16" or 24" on-center studs, any special spacing of studs for shower, toilet, sink, etc.. I am thinking the "top plate" should be 2"X8" so I have a nailer for the 5/8" Green Board.

For the education of anyone following this thread, and thinking about building a cabin, I should point out that you NEVER want any plumbing in a exterior wall, if there is any chance of freezing weather, or the pipes could freeze & break open.

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## Rick

Folks in Florida learn that about every other year. :Innocent:

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## NightShade

good lesson of exterior walls!
As long as pipe fits in wall, Spacing of studs shouldn't effect plumbing.......

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## NightShade

Just dont put a stud dead center of a valve or fixture....

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## Sourdough

Thanks NightShade.

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## hunter63

> Just dont put a stud dead center of a valve or fixture....


LOL, LOL, I just thought that was part of it, you can measure, and measure, and lo and behold, just when you thought everything was cool, dead center in the middle of a stud.
Maybe a better idea, put in the plumbing, then add studs around it.........?

Was a challenge to get everything to fit, for the lower half, drains traps, then added the vents...actually worked out well. All appliances 2", toilet 3" to 4" "stink" pipe.

When I drew up the floor plan for the cabin, the Amish construction foreman, could understand why I would want the kitchen and bathroom, back to back.

Couldn't get over the idea of eating and cooking right next to where you....well you get the idea.

Log cabins have solid exterior walls so it all had to go in a interior "wet wall" 6" studs, and as the wall has a loft over it, vent did turn 90 degrees, twice to roof, in the 4"........4 years no problem.

I did draw up my plan and have the Master plumber at work, approve it.

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## Rick

I swear if I ever build again I'll put a hallway behind the plumbing just so I can get to it.

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## Sourdough

> I swear if I ever build again I'll put a hallway behind the plumbing just so I can get to it.



The kitchen will be on the other side, and except for the Kitchen sink, that wall should be one refrigerator, and two upright freezers. That should give access to the wall if needed.

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## randyt

> I swear if I ever build again I'll put a hallway behind the plumbing just so I can get to it.


many of the commercial jobs I do there is a chase behind the plumbing. next time you're traveling and stop at a rest area check out the mechanical space behind the restrooms. many times there is a 2 foot mechanical chase.


I normally don't concern myself with stud locations. a trap will swing to one side or the other in most situations.

the log homes I've plumbed the concern was with the settling. the vent needed to go straight out so the wall would settle around the vent. if there is a offset the settling can play havoc.

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## abe

I R A PlumR 2. Won't put in my 2 cents the OP is probably confused as hell right now.

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## Sourdough

> I R A PlumR 2. Won't put in my 2 cents the OP is probably confused as hell right now.



NOPE, I installed the vent last week, it was easy.

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## abe

> NOPE, I installed the vent last week, it was easy.


Good deal, its pretty simple to figure out, but don't tell my customers. :boxer:

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## Sourdough

> Good deal, its pretty simple to figure out, but don't tell my customers.



This week I am running the 4" ABS waste line between the septic tank and the buildings. Sadly I don't have a back-hoe, so I have to dig the trench with the Case 450B Dozer.

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## abe

Have fun, don't forget to put in some clean-outs. Just out of curiosity, what is the frost/freeze line in your part of Alaska?

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