Installing an AAV under kitchen sink with a S-Trap.

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TK3000

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Hello Folks,

In my home, I installed a garbage disposal about 15 years ago, back then I was more ignorant regarding different aspects of code and my priority was to save storage space and have something functional – never had any problems concerning draining, odors, etc; always worked really well (but I almost never use the garbage disposal and the food debris and left overs I always throw in the garbage can).

A day ago, since I had to wait for some other work to be done (exterior work) and did not have much to do, I went ahead with the reconfiguration of the plumbing setup under the kitchen sink and installed an AAV (my kitchen sink have an S-Trap, it was like that since the condo was built back in 1974)

Following was the previous setup or plumbing contraption under my kitchen sink:
LANSING_OLD_UNDER_KITCHEN_PLUMBING_SETUP.jpeg


Once the previous plumbing setup was removed, there was only a stub of 1 ½ PVC cropping up from the cabinet floor:
LANSING_CONDO_KITCHEN_ADMITTANCE_VALVE_INST1.jpg


I used an oscillating tool to cut the pipe (pipe cutter could damage the pipe considering how old it is, even though it is not cpvc). Not a perfect cut (odd position to cut); then cleaned, deburred and sanded the pipe; it looked good enough to me.


Below the kitchen sink (down in the basement), the pvc drain pipe that goes up to the kitchen sink:
LANSING_CONDO_KITCHEN_SINK_PLUMBING_BASEMENT2.jpg

There is no much in terms of support (hangers, clamps or bracket), so I was considering installing some type of support in the kitchen cabinet itself; maybe a pipe riser clamp? Also, the pvc stack with the AAV is not straight, but tilted a little towards the left.

That pvc stub tended to move, so I used a clamp to hold it in place. The problem is that on occasion of gluing the pvc stack with the AAV, that clamp made things more difficult and during the process of gluing the stack it caused more problem than helped and also slow me down (pvc cement cures very fast) and I was affraid that putting too much pressure on the pvc stub could crack it, so I ended up doing things in big rush and made fatal mistake of gluing the sanitary tee upside down (only found out about it when I tested the whole thing, 10 min afterwards):
LANSING_CONDO_KITCHEN_ADMITTANCE_VALVE_INST3.jpg



As a result, I had to cut the stack and reinstall it using coupling fittings and had a purple blood mess. But everything is working as it is supposed to be. Is anything wrong in having so many coupling fittings in such a small stack?
LANSING_CONDO_KITCHEN_ADMITTANCE_VALVE_INST4.jpg



That is the end result:
LANSING_CONDO_KITCHEN_ADMITTANCE_VALVE_INST5.jpg


By the way, it does not "need" the clamp; but it seems to give more stability. I was considering using some type of pvc pipe riser clamp at the bottom of the stack. My understanding is that there must be a clearance of at least 2 inches of off the AAV itself, but there are flexible water lines move very near the AA (should they be rerouted or are they a problem). Other than that, it seems to working well with no leaks, etc.

In the basement, the pvc drain pipe that protrudes inside the kitchen sink cabinet run for about 10ft without any hanger or mounting support. Maybe a pipe mount support attached to the floor joist in the basement, like the following would be an option:

LANSING_CONDO_KITCHEN_SINK_PLUMBING_BASEMENT_PIPE_SUPPORT_OPTION.jpg


Any insights would be appreciated.
 

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Taylorjm

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I had a similar s trap setup as you and I did something very similar. The only thing is you seem to have a lot of slip fittings. It’s hard to see what I did but the main line going down is in the right back corner with the aav at the top of that line by the sink. I don’t have any slip fittings after the trap.
 

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TK3000

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I had a similar s trap setup as you and I did something very similar. The only thing is you seem to have a lot of slip fittings. It’s hard to see what I did but the main line going down is in the right back corner with the aav at the top of that line by the sink. I don’t have any slip fittings after the trap.

After the P-Trap there is only the wall tube which connects to the sanitary tee through a trap adapter.

One of the problems is that I had to redo the pvc part (pvs stack with the AAV) due to have put things in the wrong position (sanitary tee), so had to use more coupling fittings and ended up with an ugly blood purple mess. Also, the pvc stack is tilted slightly towards the left (I believe there the max angle allowed is 15 degrees) and that may be a function of the fact that there is no much support for the pvc pipe.
 

Taylorjm

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After the P-Trap there is only the wall tube which connects to the sanitary tee through a trap adapter.

One of the problems is that I had to redo the pvc part (pvs stack with the AAV) due to have put things in the wrong position (sanitary tee), so had to use more coupling fittings and ended up with an ugly blood purple mess. Also, the pvc stack is tilted slightly towards the left (I believe there the max angle allowed is 15 degrees) and that may be a function of the fact that there is no much support for the pvc pipe.
I don’t see anything wrong with the purple pvc stack part. I was taking about before the trap. There’s a lot of slip connect fittings. You could simplify it with the tee in the middle dropping down to the trap similar to the picture I posted.
 

tafisa

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Hello Folks,

In my home, I installed a garbage disposal about 15 years ago, back then I was more ignorant regarding different aspects of code and my priority was to save storage space and have something functional – never had any problems concerning draining, odors, etc; always worked really well (but I almost never use the garbage disposal and the food debris and left overs I always throw in the garbage can).

A day ago, since I had to wait for some other work to be done (exterior work) and did not have much to do, I went ahead with the reconfiguration of the plumbing setup under the kitchen sink and installed an AAV (my kitchen sink have an S-Trap, it was like that since the condo was built back in 1974)

Following was the previous setup or plumbing contraption under my kitchen sink:
View attachment 104620

Once the previous plumbing setup was removed, there was only a stub of 1 ½ PVC cropping up from the cabinet floor:
View attachment 104621

I used an oscillating tool to cut the pipe (pipe cutter could damage the pipe considering how old it is, even though it is not cpvc). Not a perfect cut (odd position to cut); then cleaned, deburred and sanded the pipe; it looked good enough to me.


Below the kitchen sink (down in the basement), the pvc drain pipe that goes up to the kitchen sink:
View attachment 104626
There is no much in terms of support (hangers, clamps or bracket), so I was considering installing some type of support in the kitchen cabinet itself; maybe a pipe riser clamp letra invisível 2025? Also, the pvc stack with the AAV is not straight, but tilted a little towards the left.

That pvc stub tended to move, so I used a clamp to hold it in place. The problem is that on occasion of gluing the pvc stack with the AAV, that clamp made things more difficult and during the process of gluing the stack it caused more problem than helped and also slow me down (pvc cement cures very fast) and I was affraid that putting too much pressure on the pvc stub could crack it, so I ended up doing things in big rush and made fatal mistake of gluing the sanitary tee upside down (only found out about it when I tested the whole thing, 10 min afterwards):
View attachment 104623


As a result, I had to cut the stack and reinstall it using coupling fittings and had a purple blood mess. But everything is working as it is supposed to be. Is anything wrong in having so many coupling fittings in such a small stack?
View attachment 104624


That is the end result:
View attachment 104627

By the way, it does not "need" the clamp; but it seems to give more stability. I was considering using some type of pvc pipe riser clamp at the bottom of the stack. My understanding is that there must be a clearance of at least 2 inches of off the AAV itself, but there are flexible water lines move very near the AA (should they be rerouted or are they a problem). Other than that, it seems to working well with no leaks, etc.

In the basement, the pvc drain pipe that protrudes inside the kitchen sink cabinet run for about 10ft without any hanger or mounting support. Maybe a pipe mount support attached to the floor joist in the basement, like the following would be an option:

View attachment 104628

Any insights would be appreciated.
My bathroom sink contains an s-trap, see attached picture. Is it possible to make this setup legal? Is an s-trap configuration with an Air Admittance Valve legal? Other suggestions?
 

Reach4

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My bathroom sink contains an s-trap, see attached picture. Is it possible to make this setup legal? Is an s-trap configuration with an Air Admittance Valve legal? Other suggestions?
fake
 

TK3000

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My bathroom sink contains an s-trap, see attached picture. Is it possible to make this setup legal? Is an s-trap configuration with an Air Admittance Valve legal? Other suggestions?

I believe that it is legal in almost all States (last time I checked, it is not legal in Minnesota). The deployment of the AAV avoid the issues posed by having a S-Trap without incurring in the costs associated with some major plumbing work. You still need at least one vent stack going outside (release of sewer gases, etc)
 

TK3000

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I don’t see anything wrong with the purple pvc stack part. I was taking about before the trap. There’s a lot of slip connect fittings. You could simplify it with the tee in the middle dropping down to the trap similar to the picture I posted.
Ohh, ok, I see your point. Your setup is better, it allows for optimization of the storage space under the kitchen sink cabinet. I am not sure if there would enough depth (horizontal distance between the pvc aav stack and the vertical tail pipe coming from the sink) in my case to do something similar -- I will check later.
 

TK3000

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Ohh, ok, I see your point. Your setup is better, it allows for optimization of the storage space under the kitchen sink cabinet. I am not sure if there would enough depth (horizontal distance between the pvc aav stack and the vertical tail pipe coming from the sink) in my case to do something similar -- I will check later.

EDIT: I did check it and there is not enough room for that in my case (J-Bend and elbow together are 6 inches in length), unless I would move the pvc pipe cropping up from the cabinet floor backwards 3 inches (too much work).
 

TK3000

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On another note, I am planning on using mounting brackets to give more support to the 1 ½” drain pipe down in the basement and help with draining the drain pipe (its angle is slightly off, not favoring good drainage). The pipe mounting brackets I have are adjustable, but not long enough when fully extended. The pvc drain pipe travels more or less parallel the the floor joists down in the basement, as shown below:

LANSING_CONDO_KITCHEN_SINK_PLUMBING_BASEMENT_PIPE_SUPPORT_DRYFIT_CLEARANCE.jpg



Pipe support mounting bracket:
Mounting_Pipe_Support.jpg


Would there be anything wrong as far as code is concerned in using a small piece of 2x4 (6 or 8 inces) screwed to the floor joists and then having the mounting support bracket supporting the pvc pipe screwed to the piece of 2x4?
 

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Reach4

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On another note, I am planning on using mounting brackets to give more support to the 1 ½” drain pipe down in the basement and help with draining the drain pipe (its angle is slightly off, not favoring good drainage).
You want to raise that pipe by something like 1/4 inch? How about lifting from above? Is the bottom shelf of the sink sturdy?
 

TK3000

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You want to raise that pipe by something like 1/4 inch? How about lifting from above? Is the bottom shelf of the sink sturdy?


I used a basic small level to visualize the pitch, it is pitched the wrong way. At this time and where I am (over 100 miles away from my new home), I don’t have means to measure it with precision. Below is a pic:

LANSING_CONDO_KITCHEN_SINK_PLUMBING_BASEMENT_PIPE_PITCH_WRONG_WAY_.jpg


The arrow points towards the direction of the kitchen sink cabinet. The length of the pipe is between 7 and 8 feet. If I would raise the pipe next to to point of entry into the sink cabinet by 3/4 of an inch using the clamp support (attached to the joist), the level would be leaning more towards the other way (but more or less in the middle); at least better than what it is now -- I don't want to put too much strain on the pipe. Also, I believe that code requires a horizontal run to have support every 4 ft (and there is none there).


Yeah, the bottom shelf is sturdy. I did look for riser clamps, but could not find one in any store nearby for that size of a pipe.

Which approach would be better?
 

Reach4

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You want that to slope 1/4 inch per foot or more (2%). If it is now 1/4 inch per foot the wrong way, you would have to lift the right side by 3.75 inches.

Reasoning: 1/4 inch per foot * 7.5 feet is 1.875 inches. Twice that is 3.75.

Also note that the bend should be a long curve bend.

So you may have a problem with raising things that much. Can you lower the left side maybe?

If you could up the pipe to 3 inch, you could use 1/8 inch per foot slope. But that pipe is much bigger, so that is not going to help.
 

TK3000

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You want that to slope 1/4 inch per foot or more (2%). If it is now 1/4 inch per foot the wrong way, you would have to lift the right side by 3.75 inches.

Reasoning: 1/4 inch per foot * 7.5 feet is 1.875 inches. Twice that is 3.75.

Also note that the bend should be a long curve bend.

So you may have a problem with raising things that much. Can you lower the left side maybe?

If you could up the pipe to 3 inch, you could use 1/8 inch per foot slope. But that pipe is much bigger, so that is not going to help.


I own this place since 2010, it is a condo and the dwv and water lines is the association's responsibility. Having said that, I never had an issues with drainage and only installed the AAV because it seemed to be the proper thing. Neither have I had any issue with kitchen sink not draining properly or with odors (but I almost never use the garbage disposal). Problem be that the association is very problematic (some board members are fighting each), and I can not wait forever. In consequence, I don’t want to change anything with the main parts of the dwv. -- other than add some supporting brackets in order to at least improve upon what is there now.

The following is the other end of the drain pipe coming from the kitchen sink and connected to the main drain line stack (which then goes underground):
LANSING_CONDO_KITCHEN_SINK_PLUMBING_BASEMENT1.jpg
 

TK3000

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So based on this, I would just elevate the under-sink side whatever you can.

I would consider a "riser clamp" in the bottom of the sink cabinet. https://www.homedepot.com/p/PLUMBFLEX-1-1-2-in-Riser-Clamp-in-Epoxy-Coated-Steel-112CLRSEP/309747775


Maybe a strap farther downstream.


Thanks for the links!

Interesting, I did a search on homedepot website for something like “1 ½ pipe riser clamps” or some other variations of that and I got a riser clamp very similar to yours (maybe a different brand), but it was not available any longer. I probably will get the riser clamp too (not available in stock at a local store), just for good measure. In any case, I already have the mounting bracket at hand (showed in my previous posts). Would there be anything wrong (mainly code related) in using a small pieces/block of 2x4 and the mounting clamps to secure the pvc pipe to the floor joist?

The pvc drain pipe is below the level of the joist, so straps could only be used if screwed to the subfloor boards (probably not a viable solution)

EDIT: my bad, the straps could be screwed to the side surface of the joist too. So, that could work.
 
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Reach4

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The pvc drain pipe is below the level of the joist, so straps could only be used if screwed to the subfloor boards (probably not a viable solution)
I think it may viable to screw into the subfloor, but don't penetrate too high.

What is the profile of your flooring? from bottom up, 1/2 inch plywood subfloor, floor tile, or maybe subfloor, sleeper space, hardwood flooring? Seems to me that if you have sleeper space, there are more options.

I am wondering if #12, 1/2 inch long screws would give enough pull.

If nothing else, you could run a 2x4 under the pipe. Maybe support that with blocks at the ends, that are screwed into the centers of thhe joists. Maybe https://www.homedepot.com/p/Simpson...-Hanger-for-2x4-Nominal-Lumber-LU24/203302252 or other Simpson-Strong-Tie product https://www.homedepot.com/b/Building-Materials-Building-Hardware/Simpson-Strong-Tie/N-5yc1vZaqzsZ615?NCNI-5&searchRedirect=simpson strong-tie&semanticToken=k27r10r10f22040000000e_20250417160631008060247543_us-central1-1j82 k27r10r10f22040000000e > st:{simpson strong-tie}:st ml:{24}:ml nr:{simpson strong-tie}:nr nf:{n/a}:nf qu:{simpson strong-tie}:qu ie:{0}:ie qr:{simpson strong-tie}:qr&sortorder=asc&sortby=price
simpson-strong-tie-joist-hangers-lu24-c3_100.jpg
 

TK3000

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I think it may viable to screw into the subfloor, but don't penetrate too high.

What is the profile of your flooring? from bottom up, 1/2 inch plywood subfloor, floor tile, or maybe subfloor, sleeper space, hardwood flooring? Seems to me that if you have sleeper space, there are more options.

I am wondering if #12, 1/2 inch long screws would give enough pull.

If nothing else, you could run a 2x4 under the pipe. Maybe support that with blocks at the ends, that are screwed into the centers of thhe joists. Maybe https://www.homedepot.com/p/Simpson...-Hanger-for-2x4-Nominal-Lumber-LU24/203302252 or other Simpson-Strong-Tie product https://www.homedepot.com/b/Building-Materials-Building-Hardware/Simpson-Strong-Tie/N-5yc1vZaqzsZ615?NCNI-5&searchRedirect=simpson strong-tie&semanticToken=k27r10r10f22040000000e_20250417160631008060247543_us-central1-1j82 k27r10r10f22040000000e > st:{simpson strong-tie}:st ml:{24}:ml nr:{simpson strong-tie}:nr nf:{n/a}:nf qu:{simpson strong-tie}:qu ie:{0}:ie qr:{simpson strong-tie}:qr&sortorder=asc&sortby=price
simpson-strong-tie-joist-hangers-lu24-c3_100.jpg

Thanks for links and pic.

The subfloor probably is 1/2 plywood and up top (kitchen) there is tile floor (no sure if there is backerboard). That probably is not going to be strong enough and could cause problems on the tile floor above.

I plan on using a pipe rise clamp as well. The floor joists on the other hand are very strong, but it is tight spot (even with an angle drill) and it also has electrical cables and copper pipes right below.

So, due to it be a tight spot with electrical cables, pipes right below, etc, I ended up doing something that I am not sure is code compliant (I can always undo it). There is closet framed (most of the basement is finished) right behind the spot where I want to affix the pipe clamp, so I screwed a small piece of 2x4 to the closet framing and then screwed the pipe clamp to this 2x4, as shown below:

LANSING_CONDO_KITCHEN_SINK_PLUMBING_BASEMENT_PIPE_SUPPORT1.jpg


LANSING_CONDO_KITCHEN_SINK_PLUMBING_BASEMENT_PIPE_SUPPORT2.jpg


Would that setup be considered ok?

I believe that what you refer to as “sleeper space” is part of the finished basement with the closet and bedroom behind the utility room. Only the utility+mechanical room part of the basement is unfinished.

Thanks!
 
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