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Small Cabin Forum / Cabin Construction / Help with plumbing vents
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Norsky
Member
# Posted: 3 Apr 2017 13:15
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Ok so the plan below shows our cabin layout except that the bathroom window was moved over to the kitchen and the bathtub was switched out for a shower stall. The septic tank is on the opposite side of the cabin from the Kitchen/bathroom and all the plumbing should be in the shared kitchen/bathroom wall. The main waste line runs all the way under the cabin and emerges under the kitchen where we have a small cement block room to hold our water storage tank, pressure tank, water heater and pump.
Upstairs is just a great room 24 x 17- no interior walls. We are at the point where we want to rough in some of the waste water drainage so that we can finish the interior of the outside wall but we aren't ready to hire a plumber yet.
Does the main vent line have to go straight up through the roof without any bends? Straight up from the bathroom is a bank of windows- can we make 90 degree bends to route it around windows?
The bathroom is 8 x 5 feet and the entire system is two sinks, a toilet and a shower on that 8 foot wall. Can they all share the one vent? Is two inch sufficient?
Thanks in advance for any advice you want to give us.
floor plan.
floor plan.


bldginsp
Member
# Posted: 3 Apr 2017 15:00
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Yes you can 90 the vents all you want, so long as they always slope down toward the waste so condensed water doesn't collect.

The vent trunk, if you have one only, should be the same size as the waste line that leaves the building. 3" is enough but 2" not large enough to handle multiple use.

And yes it should penetrate the roof and be at least 6" above the roof. Stinky sewer gasses will come out of it and you want those as far away as possible.

ICC
Member
# Posted: 3 Apr 2017 15:01 - Edited by: ICC
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some useful info http://inspectapedia.com/plumbing/Plumbing_Vent_Definitions.php#Sizes

http://www.plumbingpros.com/pdf/dwvents.pdf

Norsky
Member
# Posted: 3 Apr 2017 16:06
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Thank you both very much, that was helpful.

Norsky
Member
# Posted: 17 Apr 2017 16:12
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This is a rough plan- with the horizontal pipes with a slight incline. Does it look okay?
Mock vents
Mock vents


Just
Member
# Posted: 17 Apr 2017 17:34
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In Canada any trap that is within 5 feet of the main vent dose not need its own vent.

toyota_mdt_tech
Member
# Posted: 17 Apr 2017 21:18
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Quoting: bldginsp
And yes it should penetrate the roof and be at least 6" above the roof. Stinky sewer gasses will come out of it and you want those as far away as possible.


Just thinking out loud, that is the best option, but in areas of heavy snow, would if one was to cap it in the attic with an air admittance valve to keep sliding snow from shearing it off?

Norsky
Member
# Posted: 18 Apr 2017 07:12
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I think all of our traps are within 5 feet. I'm more worried about getting a good flush than I am about the gasses. We had a plumber here at home try to put in an AAV in the closet wall for the toilet rather than take the time to vent it up and out of the house and the toilet wouldn't flush with the valve on the pipe- not enough air coming in for the water to go down.

toyota_mdt_tech
Member
# Posted: 18 Apr 2017 08:43
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Norsky, maybe not a large enough vent stack size?

ICC
Member
# Posted: 18 Apr 2017 10:58
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If you are worried about snow slides install a diverter on the roof uphill of the vent stack. That works and is mandatory by code in heavy snow country and saves the bother of the valve. Valves of any kind introduce a new point to fail at some time.

Atlincabin
Member
# Posted: 18 Apr 2017 15:10
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An alternative I've used for vents is venting under the eaves or out the gables on the side of the house. More likely to get an occasional whiff of sewer gases, but if the vent is under the roof there's not much chance of snow ripping it off. Ultimately, in terms of "flush performance" as long as there is a way for the air to get into the system and enough volume of air (i.e., pipe size), the toilet should flush fine.

Norsky
Member
# Posted: 18 Apr 2017 18:13
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Right Toyota- 1.5 to 2 inches and about 8 feet?

NorthRick
Member
# Posted: 18 Apr 2017 20:06
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Quoting: toyota_mdt_tech
Just thinking out loud, that is the best option, but in areas of heavy snow, would if one was to cap it in the attic with an air admittance valve to keep sliding snow from shearing it off?


If it is a metal roof, just route it in the attic so that it penetrates the roof near the peak. If it's going to be a shingled roof, the snow won't slid and it doesn't matter where it comes out.

toyota_mdt_tech
Member
# Posted: 18 Apr 2017 21:46
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Quoting: Norsky
Right Toyota- 1.5 to 2 inches and about 8 feet?


I know toilets usually use a 3" but near bathrooms, I always see the 1.5" vent coming out of the roof. Seems small. As fro the length, probably not critical like tghe diameter is.

bldginsp
Member
# Posted: 18 Apr 2017 22:19 - Edited by: bldginsp
Reply 


Toilet vents should always be at least 2" all the way up.

Toyota- air admittance valves are problematic. They let air in, but not out. Vents need to do both. When you flush the toilet a large inrush of water enters the drain line and the displaced air needs somewhere to go or else it resists the flow of the water. A vent let's this air flow out. Then, when the rush of water is past, air needs to enter the drain pipe to prevent the flowing water leaving a vacuum behind that would siphon the trap. AAVs do the latter but not the former. We don't allow them where I work.

Norsky- one issue with your picture. The vent pipe under the window must pass thru the jack and king studs of the window. If these are 2x4s, you would be cutting more than 40% of the width of the studs to get a hole big enough for the pipe. That's against code, because it weakens the stud. If they are 2x6, no problem. One solution is to run the pipes on the inside of the studs, if a cabinet will be there, and cut the cabinet back to accommodate. Another solution is to use a "stud shoe" which is this metal bracket that fits around the studs and, supposedly, repairs their strength. But I think they are funky, and basically I wouldn't compromise the strength of an exterior wall for the sake of a vent. You can also install a loop vent, but they must be done correctly and half those I see are not. You can also run the vent outside the wall on the exterior, if you don't mind how it looks. No danger of freezing with vents.

If you are in freeze territory, it's a good idea to locate any underfloor vents as far away from underfloor shower traps as possible, at least 6 feet, so they won't freeze even when the cabin is heated.

bldginsp
Member
# Posted: 18 Apr 2017 22:27
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Is the glass in the windows by the stairs safety glass? Don't want some kid falling through non-safety glass...

Norsky
Member
# Posted: 19 Apr 2017 08:06
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Thanks bldginsp- they are 2x6 exterior walls all throughout the cabin. We are definitely in freeze territory and will have to drain all lines before freeze up so that's good to know about the underfloor vent.
I'm not sure on the safety glass but that's a good thought as we plan to have grandkids up to stay so if it isn't maybe figure out a fix for that ie. interior shutter on the bottom half.

bldginsp
Member
# Posted: 19 Apr 2017 08:46
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It's expensive Norsky, but the only fix is safety glass. Shutters will be open leaving the glass exposed.

When non-safety glass breaks, it produces large sharp shards that are like knives. Don't risk it.

Norsky
Member
# Posted: 19 Apr 2017 09:09
Reply 


Gotcha- thanks.

WilliamVue
Member
# Posted: 8 Jan 2018 06:36
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Have you consulted the professionals? It is always good to let this type of complicated matters handled by the professional as they are expert in dealing with it. My uncle faced the same issue and he decided to consult plumbing repairs Bergen county NJ experts for the safe repair!

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