Help on kitchen sink S trap

[Luberhill]

Great site !
Always a lurker now a poster !
Ok have a 1956 ranch that has a slow draining kitchen sink.
This whole house only has one vent thru the roof and it’s 25 ft away from the kitchen sink.
Kitchen sink is double basin with the drain thru the floor of the cabinet right below and between the double sink.
So it’s an S trap that then goes thru the floor and has another trap below it that the dishwasher drain ties to.
We never get sewer gas ever but the kitchen sink drains slow .
If just running water down it’s fine .
So....
Is there a way to use an AAV off the vertical ??
There is NO way of venting thru the roof .
AAVs are legal here but I’m not sure how to install ..
All other fixtures are close to the vent so zero issues.
Thank you and again I know this is an incorrect way to drain but it’s been this way for 60 years

 

[JG plumbing]

This is how I do it, when the inspector approves. You'll have to use a different tailpiece (one with a dishwasher inlet built in). Double basin would be similar.

 

[Jeff Handy]

Yes, remove the second trap down in the basement.

 

[Luberhill]

Would this work

 

[Luberhill]

Yes, remove the second trap down in the basement.

The second trap I think protects the dishwasher

 

[Jeff Handy]

You can’t have two traps in a row.

Maybe that is causing your slow draining, along with the need for the aav vent.

In your diagram, replace the part marked “tailpiece” with a dishwasher tailpiece.

It has a short stub to attach the dishwasher drain onto it.

The dishwasher drain has to first go high up onto the back wall of the cabinet, then bend back down and attach to the new tailpiece.

This acts like a trap, and keep sewer gas out of the dishwasher, and helps prevent a backed up sink drain from running into the dishwasher.

You will probably need to lower the location of the trap, to let the new tailpiece be long enough.

 

[Jeff Handy]

 

[Jeff Handy]

If you have a disposal, the dishwasher drain can go into that.

Post some pics of everything under your sink.

Also of the drain pipes and trap just below it, in the basement.

 

[Mitchell-DIY-Guy]

Would this work

Look at the photo that JG supplied; that’s your answer. An S-trap is not.

 

[Luberhill]

I’ll post pics of what I have
Remember it’s a double basin sink with the drain hole right below and center between the two basins
Not like JGs pic
Thx

 

[Luberhill]

Ok here’s what I have , excuse the messy under sink shot
The brass trap is right below the sink cabinet and you can see the dishwasher drain to the left of the trap in the 1/2 “ copper line

 

[Mitchell-DIY-Guy]

You need to use JG‘s picture as a guide to offset the plumbing so you can install the P-trap. No plumbing inspector will allow an S trap these days because they are known to call siphoning. Consider going to a single bowl sink as well because double bowl sinks are so yesterday; they cannot accommodate cookie sheets or things like that. If you’re not having it inspected well it doesn’t really matter what you do.

 

[Luberhill]

Yea it won’t be inspected , every house in this tract was done the same way .
They do t even inspect when they are sold
That sink is new .. my wife got rid of that single basin sink ,,, she hated it

 

[Mitchell-DIY-Guy]

Listen you keep an s trap and its problems or you go to a P-trap; it’s your choice. Part of the problem with the S trap is that it can’t really be vented properly that’s why they were prohibited by the universal plumbing code. And because of that vent issue the water in the trap can be siphoned out. If you’re doing any work on this you may as well do it correctly...

...and I can’t believe that the houses are not inspected when they are sold! that’s pretty standard almost everywhere, I need in some cases a requirement of the mortgage lender.

The fact that it’s 60 years old and every other houses like that isn’t really the point; a lot has changed in 60 years. Like we went to circuit breakers instead of fuses, and we went to grounded electrical systems... And we went to P traps

 

[JG plumbing]

Would this work

No it won't.

Picture what happens when you get a plug in the common piping. Water will come pouring out of the aav. Any aav is actually supposed to be above the counter, 6" above actually. Inspectors may let you get away with putting them as high as possible under the sink.

Do what my first picture shows. Pretty simple.

 

[Luberhill]

No it won't.

Picture what happens when you get a plug in the common piping. Water will come pouring out of the aav. Any aav is actually supposed to be above the counter, 6" above actually. Inspectors may let you get away with putting them as high as possible under the sink.

Do what my first picture shows. Pretty simple.

I’m not really sure how to do what you pictured as my sink isn’t like that one and my hole/ drain is right under and center the sink zz

 

[Luberhill]

Listen you keep an s trap and its problems or you go to a P-trap; it’s your choice. Part of the problem with the S trap is that it can’t really be vented properly that’s why they were prohibited by the universal plumbing code. And because of that vent issue the water in the trap can be siphoned out. If you’re doing any work on this you may as well do it correctly...

...and I can’t believe that the houses are not inspected when they are sold! that’s pretty standard almost everywhere, I need in some cases a requirement of the mortgage lender.

The fact that it’s 60 years old and every other houses like that isn’t really the point; a lot has changed in 60 years. Like we went to circuit breakers instead of fuses, and we went to grounded electrical systems... And we went to P traps

Yea I hear ya .. most of these houses still have fuses and don’t change when selling them either ..
I understand the s trap , I probably never get sewer gas because there is another trap below it ??
I’ll see if I can figure a way to do it like the other guy posted
Thx

 

[Luberhill]

No it won't.

Picture what happens when you get a plug in the common piping. Water will come pouring out of the aav. Any aav is actually supposed to be above the counter, 6" above actually. Inspectors may let you get away with putting them as high as possible under the sink.

Do what my first picture shows. Pretty simple.

Question , what would stop water coming up the aav in your pic?

 

[JG plumbing]

It would have to fill the Entire sink. That's why it's actually supposed to be above the counter. It would over flow the sink and not come out of the pipe.

 

[JG plumbing]

Based on your questions and what your saying you may want to just have someone do it for you. It wouldn't cost more than a few hundred.