Kitchen Sink Odor

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Stevecater

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Hi

I installed a double bowl sink about 5 years ago.
A year or 2 in the bowl farthest from the trap had a rank odor, like something decaying.
It was detectable on the left but not as bad.

I will attach a pic for clarity.
The left bowl is closest to the trap.
The dishwasher hose has a loop/trap in it and it doesn't smell when you take a whiff inside so shouldn't be the DW.
The drain connection enters the cabinet about 6" to the left of the left hand sink through the back wall.
The left sink drain from the tailpiece takes a 90 straight back then 90 down into the top of a tee-wye and straight down to the trap.
The right sink takes a 90 straight back, then 90 left into the branch of the Tee-Wye with about 1/4" slope towards the trap.

When I installed the sink, I did this to create a little extra usable space, instead of connecting the 2 bowls directly inline.

I did take it apart once and there was some grease/gunk etc inside so I used my snake and cleaned out the inside which helped but not perfect.

Wondered if it could be siphoning the water out of the trap and what causes that? Although, the trap seems to have water in it when I disassembled it.
The drain runs back into the wall and down about 3ft then horizontally to the main 3".

The sink is used regularly so it's not an issue of the trap evaporating. It doesn't really smell like a stink pipe, more like rotting vegetables etc.

Thanks in advance for any input.

Steve
 

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Jadnashua

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All that distance from the bottom of the sink, around the corners, and over to the trap is essentially open to the air. Anything that sticks to the walls or at a joint or elbow will sit there and rot. That's one reason why it's good to have the trap close to the sink so the trap arm isn't long and can accumulate crud.

It's impossible to tell from the picture, but is there the proper slope all the way from the sink to the trap? You also probably would have helped if you'd used a long sweep elbow so the waste didn't slow as much, carrying the crud along further and into and through the trap. there are some rules about how many degrees the direction of the waste can change, and you may have exceeded that.
 

Mliu

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Reasonably assuming that the right sink drain is at true vertical, that would mean the lateral pipe after the first 90 (the pipe going straight back) is level with no slope -- or very little slope -- towards the drain. It's even possible that it has a negative (uphill) slope. At the very least, you can expect food waste and foul water to stagnate in that first lateral.

The second horizontal appears to be longer than 12" and, at least to my eye, doesn't look like it has 1/4" of slope per foot. I expect that crud is accumulating in there as well.

Jim also makes a good point about the short-sweep 90's, although I think that long-sweep elbows won't be enough to solve your problem.
 

Stevecater

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I get what you are both saying. That's kinda what I had figured, gunk was settling out in the pipe because of likely a combination of too much pipe, too many elbows and slope issues. The longer cross ways run is sloped, it's hard to tell with the one going straight back from the tailpiece.

So I'm going to redo this install.
What I would like to do is what is attached in the pic. I didn't have a 3d model of a P trap so I made one up out of some long sweep 90's ;)
I really don't think I have room to get long 90's in off the tailpieces so they will have to be sanitary elbows.
My question is, is it acceptable to use a combination double wye in this application and have the DW connect to the top center connection (where a vent would typically be)?
This way the trap would be as close as possible to the 2 sinks and there would be very little pipe in 'free air'.

tks
Steve

sink.jpg
 

Mliu

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I assume you are going to use a real P-trap, and the one you made in your CAD drawing was just for conceptual purposes.

I can't answer whether the double-wye would be acceptable, although I can't see why it wouldn't work. But why not attach the P-trap directly to the bottom of the double-wye and have it perpendicular to the back wall (instead of parallel to it as in your diagram)? That way you eliminate one elbow and increase the slope on your horizontal run along the back wall.
 

Jadnashua

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If you can get to the vent, you could put a trap on each sink. This would require more access in the wall, though to connect both the drain and make a new vent.
 

Stevecater

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I assume you are going to use a real P-trap, and the one you made in your CAD drawing was just for conceptual purposes.

Yep, a real one with a drain... and it will be plastic too ;)

I can't answer whether the double-wye would be acceptable, although I can't see why it wouldn't work. But why not attach the P-trap directly to the bottom of the double-wye and have it perpendicular to the back wall (instead of parallel to it as in your diagram)? That way you eliminate one elbow and increase the slope on your horizontal run along the back wall.

Good point. I will likely do it as you suggest, even less horizontal pipe in the "room side" of the trap.

The double wye as the only thing that concerns me. Only ever seen them used with a vent connected on that top port.

Thanks
 

Stevecater

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If you can get to the vent, you could put a trap on each sink. This would require more access in the wall, though to connect both the drain and make a new vent.

No wall access. All I have is the single stubout. The vent is connected directly behind the stubout in the wall.

Why would I need another vent to use 2 traps, to prevent siphoning of the other trap?
 

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Each trap in a system needs its own vent. Now, that doesn't mean it must go all the way up to the roof on its own, they can be combined, but the rules call for it to rise at least 42" or 6" above the flood plane of the fixture (whichever is higher) before it can combine back into one run.
 

Stevecater

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Each trap in a system needs its own vent. Now, that doesn't mean it must go all the way up to the roof on its own, they can be combined, but the rules call for it to rise at least 42" or 6" above the flood plane of the fixture (whichever is higher) before it can combine back into one run.

Ok, thanks. What is the reason for each trap having it's own vent, siphoning?
 

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The reason any trap needs a vent is to prevent siphoning. Generally, things will drain well without one - the speed may suck adjacent ones dry in the process.

You might be able to get by with an AAV on the right-hand sink if you gave it its own trap, but they may not be allowed where you are. An air admittance valve is a one-way air valve that will let air in, but not out, preventing any suction that could siphon a trap dry. They are also a part that wears out, so you must maintain provisions to replace them eventually.
 

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The double wye as the only thing that concerns me. Only ever seen them used with a vent connected on that top port.
I still see no reason why your double-wye wouldn't work. You may have to put an elbow on top of the wye and then connect the DW drain hose.

But the following may force a re-design of your trap arm:

UPC 1002.3: A trap arm may change direction without the use of a cleanout when such change of direction does not exceed ninety (90) degrees. All horizontal changes in direction of trap arms shall comply with Section 706.3.

and...

UPC 706.3 Horizontal drainage lines connecting with other horizontal drainage l ines shall enter through forty-five (45) degree (0.79 rad) wye branches, combination wye and one-eighth (1/8) bend branches, or other approved fittings of equivalent sweep.
 

Stevecater

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I still see no reason why your double-wye wouldn't work. You may have to put an elbow on top of the wye and then connect the DW drain hose.

But the following may force a re-design of your trap arm:

UPC 1002.3: A trap arm may change direction without the use of a cleanout when such change of direction does not exceed ninety (90) degrees. All horizontal changes in direction of trap arms shall comply with Section 706.3.

and...

UPC 706.3 Horizontal drainage lines connecting with other horizontal drainage l ines shall enter through forty-five (45) degree (0.79 rad) wye branches, combination wye and one-eighth (1/8) bend branches, or other approved fittings of equivalent sweep.

I will change my design so the trap connects directly below the double fixture fitting then rather than head back and over (2x 90's) I will angle the trap so that I only need at worst a 45 at the stubout.
I think that's the best I can do as the stub is in the corner of the cabinet so it doesn't line up with either tailpiece or in the center of them?!?

Thanks
Steve
 
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