# S to P trap convert



## petros151 (Jan 10, 2012)

in an old house where drains go thru floor is this conversion a good way to go ?


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## oh'mike (Sep 18, 2009)

Both pictures are S traps--Add a T where the right hand 90 now sits--install an AAV to the top --then you will have a P-trap

Air Admittance Valves are not code in some areas--so check first.


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## petros151 (Jan 10, 2012)

oh'mike said:


> Both pictures are S traps--Add a T where the right hand 90 now sits--install an AAV to the top --then you will have a P-trap
> 
> Air Admittance Valves are not code in some areas--so check first.


so like this?


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## oh'mike (Sep 18, 2009)

Good!! There you have it----


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## petros151 (Jan 10, 2012)

ok thanks, this looks simple to do!


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## wctekkk (May 29, 2012)

to add to petros151 30" max


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## petros151 (Jan 10, 2012)

wctekkk said:


> to add to petros151 30" max


I might be going 20" from the TEE up to the AAV so I should be fine thanks!


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## rjniles (Feb 5, 2007)

The AAV should be higher than the stand pipe.


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## petros151 (Jan 10, 2012)

rjniles said:


> The AAV should be higher than the stand pipe.


sorry newbie here. Higher than what part of this diagram....

I am putting this under the sink in a sink base cab. I cannot put things in the walls. So the sink base is up against the wall and the highest I can go with an AAV is at the top of the cab. so that would make it a bit higher than the level at which the sink connects to the drain. I have an illustration to show what I would do (have not done it yet but HOPE to do this TOMORROW) THANKS !!!


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## rjniles (Feb 5, 2007)

Your earlier posts showed a laundry standpipe not a sink. The AAV is supposed to be above the flood rim of the sink.


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## wctekkk (May 29, 2012)

2"drain would be nice


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## rjniles (Feb 5, 2007)

wctekkk said:


> 2"drain would be nice


For a laundry standpipe- yes. For a sink 1.5" is fine.


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## petros151 (Jan 10, 2012)

rjniles said:


> Your earlier posts showed a laundry standpipe not a sink. The AAV is supposed to be above the flood rim of the sink.


yes my error I started just asking about P traps and S traps in general. But in fact this is a kitchen sink set up with a D/W I'm attempting. I can quickly see I am in trouble here.

as to the AAV In my case the base cab is up against the wall and as of now there is no where to put the AAV except at the top of the cab which is below the flood rim.

so in this case is it worthless to try an AAV at all? and this another issue-- I am going to have a Dish washer drain into the same drain as the sink. here is another drawing... gulp


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## wkearney99 (Apr 8, 2009)

When the AAV is lower than the flood rim of the sink then water will overflow through it first, leading to a leak you won't seek at the sink first.


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## wctekkk (May 29, 2012)

thought he was dumping his a/w into sink. my bad


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## wctekkk (May 29, 2012)

air gap needed


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## wctekkk (May 29, 2012)

?...never used a AAV trying to picture installing one that would be above F L R and be accessible without being buried in the wall


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## VIPlumber (Aug 2, 2010)

wctekkk said:


> air gap needed


Or high loop, if allowed by AHJ.


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## VIPlumber (Aug 2, 2010)

http://www.diychatroom.com/f7/vent-requirement-laundry-washer-drain-pipe-35753/

Here's a post from a few years back on the forum that has a pretty good drawing & discussion concerning AAVs. One thing I don't like about them is that since they are a mechanical device they are therefore prone to failure more often than a conventional vent.


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## wctekkk (May 29, 2012)

VIPlumber said:


> Or high loop, if allowed by AHJ.


key words if allowed by AHJ.


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## rjniles (Feb 5, 2007)

wkearney99 said:


> When the AAV is lower than the flood rim of the sink then water will overflow through it first, leading to a leak you won't seek at the sink first.


This is true but that will only happen if the drain is clogged down stream from the trap.

Realizing that it is not code compliant, I have seen plenty of AAVs installed below sinks and they work fine. Very common in sinks located in kitchen islands or peninsulas.

Not all codes require an air gap for the DW.


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## petros151 (Jan 10, 2012)

wkearney99 said:


> When the AAV is lower than the flood rim of the sink then water will overflow through it first, leading to a leak you won't seek at the sink first.


so what about kitchen island situations how can you ever have an AAV above and flood rim in any island install? SO I guess the AAV as high a possible and a 2" drain will be my only option? would it help to put in a 2.5" drain ?


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## rjniles (Feb 5, 2007)

petros151 said:


> so what about kitchen island situations how can you ever have an AAV above and flood rim in any island install? SO I guess the AAV as high a possible and a 2" drain will be my only option? would it help to put in a 2.5" drain ?


 For a island or peninsula sink drain without an AAV, you use a "Siamese vent".


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## petros151 (Jan 10, 2012)

thanks for that input, sorry again I have been asking questions based on my knowledge and now I see my situation more clearly... there is no vent on anything on the 1st floor. I have a drawing of what I currently have- there is no vent for anything on the 1st floor. the sink drains ok sucks at the end but is not slow. 

There is a vent for the 2nd floor bath that services the sink/toilet/tub but there is no way to tie in to that you'll have to trust me the vent is above the bath which is an addition onto a 100 yr old house than had and outhouse originally. 

It's a plumbers job I know but I am trying to DIY -- I wonder if I could :

#1 put a vent out the wall and up along the outside of the house

#2 put an AAV inside the wall behind the sink

the house is a balloon frame but there are fire blocks on some so it is not always easy to go up and behind the new sink area is fire blocked -- am I whistling dixie here ?

:whistling2:


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## rjniles (Feb 5, 2007)

$1 You could install an outside stack but it will look like hell. Check with the AHJ before you do.

#2 An AAV can be installed in the wall but it needs to be accessible for maintenance. Use a return air grill or an access panel.


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## petros151 (Jan 10, 2012)

I"ll have to check to see if AAV is allowed, Studor site says they are legal in PA


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