I am upgrading an upstairs bathroom in an old victorian and I want to avoid adding new vents if possible. If I could run an unvented stack arm from the tub to the main vent stack it would ease my job, but I am getting conflicting information. The distance requred is about nine feet, but according to one source, the tub drain must be 1.5 inches and can extend a max distance of 5 feet unvented. Another source implies that I can simply up the drain pipe diameter to 3 inches to get the distance I need. I don’t see why there would be a maximum diameter to the tub drain, so a bigger pipe should solve my problem, right?
I thought the unvented stack arm distances were related to the rule of thumb about re-venting i.e. add a vent when the drop equals the pipe diameter. Am I wrong about this?
Replies
Consider this a bump as I am not a plumber.
You may wish to look into an air admittance valve. See: http://www.toolbase.org/tertiaryT.asp?DocumentID=2127
Derek
You do want to be careful to make sure that air admittance valves are approved in your jurisdiction. My NJ building inspector will not accept them.
Bob Chapman
The Idea is the Venturi Princepal kinda, That water going down tries to suck the drain dry so you have to provide more space/ air for the vacume not to be to great so as to degrade the wet seal.
AAVs are referred to as "cheater vents" in some areas. ;)
According to one manufacture they are code compliant in all states, I think I read that but they aren't the 3.99$ home desdrain type Ok depot.
could check the oatley site that s what despot has. At one time I had sent off for product info on the approved and I'm thinking?????????? ohhhh brain what was the name? something ONe or????
If you are not getting an inspection, a wet vent is fine.
Unless you are some type of nuerotic, code head who can't sleep at nite unless everything in your world is exactly as another has convinced you it should be.
Relax. We are not earthquake proofing this guys house.
Eric
I Love A Hand That Meets My Own,
With A Hold That Causes Some Sensation.
[email protected]
Hey Code head? howd yu know I got a real code in my head.
http://www.plumbingwarehouse.com/autovent.html
I think that this is the one I read about Air Admittance Valves by Studor¯:
Never heard the term 'stack arm'. Can we agree on 'trap arm?'
According to Code Check, the maximum length of a 3" trap arm is 12 feet. That part of the code anticipates a toilet being connected rather than a tub, and there might be some differences. For instance, a toilet will need to drain solids, but it will usually drain a maximum of 4 or 5 gallons of water, and probably 1.6 gallons in most situations. A tub won't have solids (hopefully... what age are your kids?) but it will drain 30, 40, or more gallons at a time, if used as a tub and not a shower. Decide for yourself whether these or other differences might matter.
Anecdotally I can tell you that our farmhouse has an unvented bathroom. The tub, toilet, and lav all drop into a 3" arm that runs several feet to a wye, the other branch of which is vented twice (once at the kitchen and once at the laundry). The tub is furthest from the wye and the run is probably about 10 feet. It works fine. Since there's about 2 feet of 1-1/2" pipe draining the tub, before it joins the 3" arm, I'm sure the 3" pipe is barely full.
So, I'd say you're OK, although I'm sure a retired-plumber-turned-inspector would bust you.