View Full Version : Sanitary Tee vs. 90 Wye vs. Vent Tee
11-09-2004, 10:26 AM
Downstream from my sink trap I am required to vent the drain - I am accomplishing this with a studor (air emittance) valve. In order to install this valve I must tee into the horizontal line. Which fitting do I use in this instance? I have been told a sanitary tee is not to code but also recall that a wye is not to be installed 'laying on its back'. That leaves only the vent tee but I think that is also a misapplication. If the wye is the correct answer, in which orientation is it to be set? Help!
A tee cannot be installed on its back, a "Y" can be, but for your purpose, since the AAV has to be vertical, a combination Y-1/8 bend would be preferable. A vent tee is just that, a vent fitting not designed for use in the drainage portion of the system.
11-09-2004, 01:13 PM
Thanks for the reply - very helpful.
I am rather curious.....
Sinks that are not vented are usually s-trapped and have no vertical. Are you sure it is not vented? Are AAVs legal in your area? Who is requiring that you vent it? Why are you not venting it correctly?
11-10-2004, 07:20 AM
The sink was a late addition to my basement. As a consequence, I did not have drain lines in the floor. Installing them would have required breaking up the concrete. As an alternative, I chose a packaged sump/pump. The sink drains to the ejector pump which pumps up to an overhead drain. The air admittance valve is legal in my area - I thought they were almost universally so now. I got into trouble because I had used a vent t to install the Studor valve. I understand that you also cannot install a sanitary t 'on its back'. Consequently, I have taken the advice of a poster and installed a y with a street 45 to get to vertical. I will find out today if it passes with the inspector but expect it will.
You do realize, don't you that the sump pump needs to be vented and you cannot use a AAV on these--they will not operate correctly?
Also in my area they do not let you install a sump because you do not want to break up the concrete. You can install an ejector only if it is IMPOSSIBLE to gravity drain, not inconvenient. Also there are still many, many places that AAVs are not legal. They also should only be used if it is IMPOSSIBLE to vent regularly, not inconvenient.
11-10-2004, 12:02 PM
The sump pump is vented normally. Now that I think about it, it may have been possible to vent the sink drain using that vent? I don't know. It certainly would have been much more difficult. I am curious about the discouraged use of the AAV - perhaps you may provide some insight. Although it would not have been impossible to find an underfloor drain to tie into, it would have been cost prohibitive and impractical. The nearest in-floor drain is approximately 30' away. In this case, I am draining a very underutilized, small wet bar sink. I understand the need for codes but issues still need to be approached practically and eventually, you do reach a point of diminishing returns.
Air admittance valves are "terminations" and not a panacea to avoid proper venting. In a closed system, such as a pump setting without a vent to the atmosphere, an AAV will "air lock" it since it cannot let air out so water can enter the system, and when that happens drainage cannot occur. The idea behind discouraging pump installations is that eventually the pump is going to fail for some reason and you will flood the area. If there is a conventional drain anywhere in the area, and the plumbing is installed properly, that problem is avoided.
My local inspector prefers a san tee on its back to a wye/combo for vertical vent-only connections to a horizontal drain because "it vents better." No doubt backed up by extensive testing in his personal hydraulics lab (not). I'm sure the guy who replaces him will go around town hassling plumbers for installing san tees on their backs. So it pays to run your plans by your local inspector, especially if you're doing something for the first time, regardless of what code or common sense might otherwise suggest.
The Illinois Plumbing Code prohibits all mechanical venting including AAVs. Of course, all the home stores here sell Studor vents anyway--go figure.
11-14-2004, 10:46 AM
I am very weak on venting knowledge,so recently on recommendation of someone on this forum, I read two articles("back to basics:venting") in the June '03 and October '04 issues of PMengineer ( www.pmengineer.com). Very helpful, but also very technical. I never knew how technical venting can be!
One thing I noted in these articles and in some references they cite is that engineers are in love with AAV. They think they are wonderful; they think that as long as the device is certified by ASME or whatever, it will be fine and nobody will be killed by SARS or sewer gasses. They are very critical of the code authorities for being so "stubborn" and slow to approve.
I am in no way offering this as MY opinion; just passing along as very interesting for those who care to read and comment.
But if you also noticed in the articles, it mentioned that the AAV was a "terminal" which was added after the fixtures were vented properly, and the AAV was never intended to be fixture vents to the exclusion of a proper vent system. Engineers fall in love with a lot of things that make their lives easier and the building cheaper. But they also feel that they are the only ones qualified to create a proper system. Which is why they were so "put out" by the UPC not allowing "radical" venting systems if an engineer designed it.
11-16-2004, 07:59 AM
Thankyou for the link to the PM site. The articles were very informative. You may also do a search for 'air admittance valves' which will return many articles. Apparently, this has been a hot topic for many years in the plumbing community. As you may have gathered, I am a bit of a newbie with plumbing systems (obviously, I am not a plumber). Interestingly, in addition to posting a question in this forum, I also asked a number of plumbers about the AAV and the corresponding fittings. The answers varied by individual. Many thought the sanitary t should be used while others were adament about the use of a y. In the end, the local inspector approved my use of a studor valve in the horizontal portion of the drain, just downstream from the trap fitted with a y. Thanks for all the posts.
11-16-2004, 12:13 PM
Jim, let us also recognize that the PM columnist is a long time lobbyist to the code making bodies and has been fighting for the AAV's for decades. If you go to IAPMO's site and click on the Report on Proposals 2004 you will read his supporting documents and continuous efforts. Harry's comments on the Philadelphia system resulted in my spending over four hours reading on line articles from PM. You are lucky to have kept yourself to only two articles.
01-03-2010, 08:09 PM
AAV's need to be accessible.
You can't hide them in walls.
If you place them in a wall, there needs to be a panel that lets air in, or the AAV doesn't work.
Some people use heating vent covers. (Grills)
If you have access to the wall, it's more effective, and costs less to use solid venting with pipes.