Should I add an AAV to my single bowl kitchen sink?

[CountryBumkin]

I am doing some plumbing rework on my Kitchen sink because I replaced the shallow double bowl sink with a deep single bowl and now the disposer outlet is lower than the p-trap connection.

Since my plumbing comes out of the slab, I can cut down the existing 3" pipe and install a new sani-tee lower down. That solves the disposal drain height issue.

But I'm wondering about venting the new sink drain. This is an island Sink so the existing vent is in the wall about 6ft from the sink itself.

Since I switched from a double bowl sink to a single, I'm wondering if I should add (or need) an Air Admittance valve. In a double bowl setup does the adjacent bowl act as a vent for the bowl that is draining?

If I need an AAV, I could use the "unused" 1-1/2 connection on the left side of the sani-tee to add the AAV. If this is a good idea, I would add enough pipe to get the AAV to the highest possible point under the sink (but it would still below countertop).

I don't have any drainage problems now - I just want it to be correct.

 

[Standardairconditioner]

In a double bowl setup does the adjacent bowl act as a vent for the bowl that is draining?

No.

Venting is only required and done AFTER a trap.

If your double sink was working fine before, and your single sink is working now, then do nothing.

 

[Sponsor]

 

[CountryBumkin]

Okay. Thanks.

 

[Reach4]

But I'm wondering about venting the new sink drain. This is an island Sink so the existing vent is in the wall about 6ft from the sink itself.

How does the current venting get to the wall... something like this?

If not, you need an AAV after the trap. The trap arm must stay horizontal (1/4 inch/ft slope) until the AAV.

https://terrylove.com/forums/index.php?threads/island-sink-venting.43049/

 

[CountryBumkin]

No, not like that. I have a 3" pipe coming up from concrete slab directly under the sink. There is a sani-tee fitting with a clean out cap at the top, and two 1-1/2" openings (left side is capped, right side has sink trap). There is no sign of the vent pipe inside the sink cabinet (as shown in the drawing), however there is a kitchen wall to the right of the sink island. I assume it has the vent stack, but I don't know for sure.

 

[Reach4]

There is a sani-tee fitting with a clean out cap at the top, and two 1-1/2" openings (left side is capped, right side has sink trap).

Take a look. That cap might be an AAV. If it is not, you could replace it with an AAV.

If I need an AAV, I could use the "unused" 1-1/2 connection on the left side of the sani-tee to add the AAV. If this is a good idea, I would add enough pipe to get the AAV to the highest possible point under the sink (but it would still below countertop).

Sounds like an alternative, but I am not a plumber. I don't know if that is to the rules, but I expect it would work well.

The purpose of this vent is to keep the trap from getting siphoned out-- not to make the water drain better.

 

[Standardairconditioner]

I switched from a double bowl sink to a single

Why do you feel you need to ADD a new vent now with a single sink, if there were no problems before with the double sink?

I don't have any drainage problems now

You seem to be conflicted with what is already correct, yet risk making NEW problems when you have none.

It may be a good idea to seek a professional.

 

[CountryBumkin]

Why do you feel you need to ADD a new vent now with a single sink, if there were no problems before with the double sink?


You seem to be conflicted with what is already correct, yet risk making NEW problems when you have none.

It may be a good idea to seek a professional.

I'm not looking for new problems - just want to ask the professionals on this forum if I should add an AAV since I'm under the sink anyways. Since everything is working fine, I'm going to leave it alone. "Don't fix it if it an't broke" right?

@Reach, the cap is not an AAV. I put the cap on when I cut off the trap fitting for the second sink basin. I replaced the two basin sink with a single basin.

 

[Reach4]

@Reach, the cap is not an AAV. I put the cap on when I cut off the trap fitting for the second sink basin. I replaced the two basin sink with a single basin.

I was referring to the "clean out cap at the top".

 

[Terry]

Without a vent that goes through the roof, which an Island Vent has remotely, the other option is an AAV.
Many Island sinks in Washington are now using the AAV to vent the kitchen sink. This one has an Air-Gap on the counter. Normally those are plumbed back down to the disposal with 7/8" hose, but in this case since the drain was low in the wall, a tee was added below the disposal 90 bend. Either way works.
There is a 2" cleanout at the wall, and a hammer arrestor for the dishwasher. Someone please turn the hot supply back on for the dishwasher.

On a rental I stayed at.

 

[Jadnashua]

WIthout a vent, you may end up with it being the equivalent of an S-trap. An S-trap can literally drain too fast, sucking itself dry. The vent is needed to break the suction so that doesn't happen. So, if your p-trap just turns down into the drain without a vent coming off first, yes, you should add an AAV or plumb in an atmospheric vent. The picture Terry showed has an offset in it, partly to avoid covering the electrical outlet, it seems. Anything at least 45-degrees up will work. You want the AAV as high as you can get it in the cabinet while still being able to unscrew it for eventual replacement when it fails.

 

[Master Plumber Mark]

Without a vent that goes through the roof, which an Island Vent has remotely, the other option is an AAV.
Many Island sinks in Washington are now using the AAV to vent the kitchen sink. This one has an Air-Gap on the counter. Normally those are plumbed back down to the disposal with 7/8" hose, but in this case since the drain was low in the wall, a tee was added below the disposal 90 bend. Either way works.
There is a 2" cleanout at the wall, and a hammer arrestor for the dishwasher. Someone please turn the hot supply back on for the dishwasher.

Thats real pretty... I dont understand why the dishwasher is not tied into the easy outlet on the disposal??
Either way it will work,, just wondering if it has something to do with code in Seattle ?? The AAV vent is ok but here in our town they want the things as high as they possibly can be crammed up under the sink.....
something to do with being above the flood rim of the fixture.....
I think the hammer arr-ester is a waste of money-- but it all looks freaking great from my house.....

 

[Terry]

Thats real pretty... I dont understand why the dishwasher is not tied into the easy outlet on the disposal??

With the boxy and deep sink, adding the outlet that I could swivel and drop down lower meant for a nicer loop from the air-gap.
Normally I always knock out for the disposal hookup, but since I had the depth to work with, and being an odd sink, it worked out for the best. Otherwise the pressure on the plastic air gap was going to have a hard time staying fastened at the top.
How often have I done this Mark? This was the first time. I have been thinking about doing this for my sink at home so that I don't have to drain through my disposer. Not everyone in my home runs the disposer to clear it before turning on the dishwasher.

 

[Master Plumber Mark]

It is just fine with me ---- it really all depends on how dirty you throw your dishes into the dishwasher
My wife will put them into the dishwasher literally covered with dried on bean gunk ect and expect
the dishwasher to scour them off......

I have heard that the dishwasher can throw will throw a lot of these particles into the
drain as large as a baked bean coming off the dishes, or eggs or bacon... The idea of it
going through the disposal is to catch all this junk and grind it up better before going down the drain

both ways work just fine, in colorado they expect you to install an Air gap on the sink which you
tie in the dishwasher line to then go down into the disposal... this was pretty dumb but that is how
it was when I was working out there years ago...

 

[Terry]

both ways work just fine, in colorado they expect you to install an Air gap on the sink which you
tie in the dishwasher line to then go down into the disposal... this was pretty dumb but that is how
it was when I was working out there years ago...

I knew a single woman that ran her dishwasher every five days. By the 5th day the water was almost leaking out of the door, dark, mucky and smelly.
I installed an Air-Gap on her sink and that solved the problem. She no longer was filling up her dishwasher from left over disposer water.