Kitchen sink - one trap or two?

[Carson Dyle]

I have a kitchen sink with two bowls, a disposal on the left, drain on the right. The plumber who installed the disposal chose to put in two traps, connect them in a Y and run it into the drain on the back wall.

The thing that annoys me about this is that the traps use up a lot of under-sink storage space. The one on the disposal is placed toward the front of the cabinet, almost completely blocking the space on that side. Could this have been plumbed with a single trap? Seems to me that I've seen this in the past with the outlet from the disposal just run across into the the downtube from the other drain, and through the one trap.

 

[PowerEngineer]

Yes, I've seen a sink and disposal plumbed to a single trap. There's an example under my own kitchen sink! 😉

Actually, I wish I had two traps. When the disposal occasionally packs the trap full of debris, it'd be nice if the mess didn't immediately back up into the sink next to it. My two cents...

 

[NetWareHead]

Textbook answer: each trap needs its own fixture arm with their own vents and double traps on one arm are not allowed.

Realistic answer: You only need 1 p-trap which can service multiple sinks. However. some jurisdictions expressly demand the disposer have its own trap.

IMO, the single trap is the best way to go. It will receive flow from 2 sinks and any remaining ground food in the trap will be washed away.

Check this graphic: http://i577.photobucket.com/albums/ss216/LazyPup/PLUMBING ILLUSTRATIONS/disposaldrainconnection.jpg

 

[Carson Dyle]

One thing I do notice that's different (better?) is that in this setup I never see water rise into the open bowl when the disposal sends waste and water into the drain at a high rate.

 

[NetWareHead]

You may have a clog somewhere in your line. The single trap gives you the ability to see the symptom (backing up into other sink) whereas with the double trap, you wouldn't see it. Water will take the path of least resistance and instead of flowing down the trap, it will go into other sink. The clog is offering resistance and backing the water up int the other sink.

Fill up the non-disposal side sink completely with water, then release the drain and look at the disposer side of the sink. If water backs up into the disposer side, you have a clog somewhere. Get an electric plumbers snake and sweep the pipe.

If you don't get backup in the opposite side of the sink, the problem may be how it is piped. A pic would help.

 

[MongGrel]

The first post necro spam is pretty strong around here these days.

 

[Raj99]

Hello Experts,

I need some suggestions here. Our kitchen disposal sink doesn't connected to any P-Trap but other side sink is connected. We are smelling odor then we realized that it could be due to no P-trap to our disposal that connected to outlet to sewer. Please suggest me whether need to reconnect with 1 P-trap along with the other sink or a separate P-trap? I appreciate your help & thoughts.

 

[paperfist]

Hello Experts,

I need some suggestions here. Our kitchen disposal sink doesn't connected to any P-Trap but other side sink is connected. We are smelling odor then we realized that it could be due to no P-trap to our disposal that connected to outlet to sewer. Please suggest me whether need to reconnect with 1 P-trap along with the other sink or a separate P-trap? I appreciate your help & thoughts.

Codes is usually 2 P-Traps, but room under the cabinet can sometimes be limited.

Do you have any under cabinet pictures? If the garbage disposal line doesn't have a trap it needs one. You could possibly tie both sides together.

 

[Greenman]

Hello Experts,

I need some suggestions here. Our kitchen disposal sink doesn't connected to any P-Trap but other side sink is connected. We are smelling odor then we realized that it could be due to no P-trap to our disposal that connected to outlet to sewer. Please suggest me whether need to reconnect with 1 P-trap along with the other sink or a separate P-trap? I appreciate your help & thoughts.

1 trap works just fine. Use a baffled tee where they join and it will work like a charm. In 40 years of construction I've never seen a double bowl sink with 2 traps. It's a single fixture with 2 holes.