Why 2 traps under dual sink?

[NIXDSG]

I'm remodeling my kitchen and moving the sink. What I have now is a double sink with 2 p-traps and extra(?) vent between the traps. I ALSO have a vent under the floor up stream from the drains. A LOT of extra connections.
As best I can tell I can connect both sinks to 1 trap. Why would I want/need 2 traps?

 

[NIXDSG]

Same perspective from under the floor. Drains go away from me, vent comes toward me.

 

[Lambeau]

Here's how mine was plumbed in 2000:

 

[NIXDSG]

Searching the googles I see this a lot, none are 2 traps.

 

[Roots-type]

Traps hold water to prevent sewer gases from coming back into the house. If you took that trap off it would stink.

 

[NIXDSG]

It still has a trap, just 2 sinks attached to it.

 

[HuntFishCobra]

This is how I did mine when I added a disposal. Yes our house didn’t come with when we bought it, we’re on septic. Works perfect.

Searching the googles I see this a lot, none are 2 traps.

 

[Roots-type]

It still has a trap, just 2 sinks attached to it.

Yes I see that. They need their own individual traps or sewer gas will make its way from the main building drain, up that sink drain line, out of the sink, and into the house.

 

[HillbillyHotRod]

Not if like in post 4. That is the way ours is.

 

[Bullitt1448]

You only need one trap as long as it is between the last sink and the sewer line. No need for a trap between the 2 sinks if they are plumbed into a common sewer line

 

[03cobra#694]

When I redid our kitchen, one trap for the dual sink. That's what it had originally.

 

[OX1]

Overzealous inspector required it?, happens a lot.

 

[Weather Man]

Might be a code thing in your state or area.

 

[72MachOne99GT]

Single trap in our double sink with a disposal as well.

 

[JAJ]

Our house was built in 2001 and the one-piece double kitchen sink has a small sink with a disposer and a large sink. The dishwasher drain goes into a fitting on the disposer and the disposer drain connects to the sink downpipe above the single trap that serves all three.

The only problem with it is that occasionally, someone fills the disposer with stuff but doesn't run it. Next person along discovers the small sink won't drain, so they turn on the disposer and get a geyser of crap out of the big sink drain.

 

[93Cobra#2771]

Our house, built in 1997, has one trap. Both sinks are plumbed together and dump to one trap, similar to post #4. Only difference on ours is that the balance tube between the two sink drain lines has the trap right in the middle of it. Then the trap is connected there. So instead of exiting off the one sink, it exits to the trap right between the two sinks. No disposal on our sink.