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Thread: 2 Air Admittance Valves on double sink, IPC 2009

  1. #16
    In the Trades mtcummins's Avatar
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    I'm thinking he's more of a honey mustard type of guy...

  2. #17
    In the Trades mtcummins's Avatar
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    I talked with one of the General Contractors and the head of maintenance for one of the largest real estate companies in Pittsburgh today, who just happens to be doing a gut remodel of the house next door to mine, and he said that 2 traps and 2 vents is the normal requirement in Pittsburgh for a double sink.

    This is how their plumbers rough in a double sink for AAVs, which they had to do in their kitchen, just like my house. Picture is a little dark, but you'll see they bring 4 pipes through back of cabinet, bottoms each get a trap to sink bowl or disposal, tops go up to an AAV. This is apparently required here, as the city has the right to add to the code restrictions.

    Go figure.
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  3. #18
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by mtcummins View Post
    I talked with one of the General Contractors and the head of maintenance for one of the largest real estate companies in Pittsburgh today, who just happens to be doing a gut remodel of the house next door to mine, and he said that 2 traps and 2 vents is the normal requirement in Pittsburgh for a double sink.

    This is how their plumbers rough in a double sink for AAVs, which they had to do in their kitchen, just like my house. Picture is a little dark, but you'll see they bring 4 pipes through back of cabinet, bottoms each get a trap to sink bowl or disposal, tops go up to an AAV. This is apparently required here, as the city has the right to add to the code restrictions.

    Go figure.
    Why in the world would you use AAVs like that if you have an open wall like that? Is there a room above you that' finish dry walled? If so cut out a joist space (or atleast a hole on the bottom) and run a vent up into the attic and tie it into an existing vent.

    And the city ALWAYS has the final say because if you look in the code book somewhere it will saying to the effect that the authority having jurisdiction always has the final say. If the inspector said you could run all your drainage up hill and through a 1.5" line with no venting then by all means you could do that! However if they say you have to use all 4" piping with 8" venting then you'd have to do that too! Ok a little extreme of an example I know

  4. #19
    In the Trades mtcummins's Avatar
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    Quote Originally Posted by Doherty Plumbing View Post
    Why in the world would you use AAVs like that if you have an open wall like that? Is there a room above you that' finish dry walled? If so cut out a joist space (or atleast a hole on the bottom) and run a vent up into the attic and tie it into an existing vent.
    I don't know in his case, I didn't trace it down to see why they couldn't vent it. The whole house is gutted, and they've hard vented the laundry rooms, all the baths, etc, just not this kitchen sink. These houses are 3 stories, so the attic is either non-existent (flat roofs), or 2 stories up. I have the exact same situation, in that I was able to hard vent everything in my house while I had it gutted, but I have an exposed brick wall as my kitchen backsplash, so there was no way to feasibly route a vent line, other than to do an island loop, which I'm not too keen on either. It was literally impossible w/o completely changing the design of the house or creating a structural nightmare. I'm not sure in my neighbor's case, but they went to good lengths to vent everything else, so there must have been a good reason.

    I actually wouldn't be surprised if you start to see things like this creeping into the code, but who knows how long that will be. Pittsburgh has been requiring this arrangement for some time now, as they say its better venting - maybe they're just crazy, but I could see how it could theoretically be a better venting situation. Of course, I know nothing about code up in the frozen tundra, so maybe not for you...

  5. #20
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by mtcummins View Post
    I don't know in his case, I didn't trace it down to see why they couldn't vent it. The whole house is gutted, and they've hard vented the laundry rooms, all the baths, etc, just not this kitchen sink. These houses are 3 stories, so the attic is either non-existent (flat roofs), or 2 stories up. I have the exact same situation, in that I was able to hard vent everything in my house while I had it gutted, but I have an exposed brick wall as my kitchen backsplash, so there was no way to feasibly route a vent line, other than to do an island loop, which I'm not too keen on either. It was literally impossible w/o completely changing the design of the house or creating a structural nightmare. I'm not sure in my neighbor's case, but they went to good lengths to vent everything else, so there must have been a good reason.

    I actually wouldn't be surprised if you start to see things like this creeping into the code, but who knows how long that will be. Pittsburgh has been requiring this arrangement for some time now, as they say its better venting - maybe they're just crazy, but I could see how it could theoretically be a better venting situation. Of course, I know nothing about code up in the frozen tundra, so maybe not for you...
    Yeah sometimes it's hard or damn near impossible to get a vent up.

    But you won't see that stuff "creeping" up in the code I don't think because it's just a bit out to lunch. And yes you're right you will get better venting out of having 2 AAV but you'd also get better venting out of having 6" vents picking up all your fixtures. But you don't see inspectors making people put in 6" vents for sinks.

    But if that's the way your inspector wants it you can't really argue with them because they have the final world. The drawing you did up on your last couple of posts there will work just fine for what you need.

  6. #21
    In the Trades mtcummins's Avatar
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    Thank you all so much for your input. It was a frustrating process, learning not only more of the general code, but trying to figure out what Pittsburgh wants on top of that, but I can say that I've learned a good bit in the process, so that's always good.

    I've been looking at some posts on here about converting single to double lavs, and it seems to always be done with 2 traps and vents, though granted its often only 1.25" traps, which would reduce flow a bit. But, point being, it seems like double lavs are almost always plumbed with separate traps and vents, even if it would be feasible to trap them together. Why is that? Seems like the reasoning for this would carry over to a kitchen sink, which with everyone having disposals and dishwashers, gets a lot of abuse drain-wise. I think I'm actually sold on 2 traps and vents being worth it - it really isn't that much extra work or cost, and its only for one fixture. Even if I wasn't required to do so, I think I might do it this way.

    Agreed though that there is some point where you have to stop. I'm a fan of 2" vent and drain lines (rather than 1.5") in almost every case as well, so I guess I tend towards the overdo it to be safe end. I generally will only carry one lav on a 1.5" vent and 2 of anything on a 2", though this is conservative. My house ended up a bit like swiss cheese - lots of separate vent lines go up above the highest drain line on the 3" stack and tie in there - I also wouldn't accept a 2nd vent line protruding through the roof. My 3rd floor stack is almost more tees and wyes than straight pipe, haha. Go ahead and call me fussy, its true.

    Guess that's also why I have a home-run Pex water system with at least 2 shutoffs between every fixture and the manifold. And insulate all water pipes all the way through the house. Overkill, yes. But I'll never disrupt anything else in my house to work on something, and the hot water gets to my fixtures a lot faster, and the cold water gets there colder since it didn't absorb heat out of the walls, hot pipes, or drain lines. I also like that there are very few fittings that aren't exposed... less places to leak that are hard to get to.

    I'm not afraid to spend more time and money to get what I think is the best product, but I can definitely see how many people would not accept the cost of the way I do things. I do all the work myself pretty much, so extra time and material cost isn't that significant compared to the peace of mind I have living in a house that is done this way. To each his own...

    Anyway, thanks everyone who helped me work through this. I'll be doing it how I sketched in the one post. I can't see how it could hurt, other than a few extra dollars in parts and maybe a little less room under the sink.

  7. #22
    Moderator & Master Plumber hj's Avatar
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    Now you are trying to confuse the issue. The ONLY time two lavatories are connected using ONE trap, is when a handyman/homeowner does the installation. THAT IS NOT the same as a double kitchen sink.

  8. #23
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by Rich B View Post
    This website and the pictures might give you some ideas that help:
    http://www.hammerzone.com/archives/k...eplace_old.htm
    Wow interesting link...
    I have never seen anyone apply teflon paste on a galvanized pipe before putting on a Fernco...

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  9. #24
    Forum Admin, Expert Plumber Terry's Avatar
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    Where is the peanut butter and jelly?


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