Dual P-traps for Kitchen Sink?

By definition and current IBC, would you consider this a Double Trap on this Kitchen Sink? The current code here in CO is somewhat contradictory depending on how you read the different sections. Just wondering what some of your opinions would be on it. Been seeing it a lot lately…

I myself would not say double trapped but I’m also not going to say it is correctly installed.
Let’s find out.

Do you have a pic of the piping behind the disposal?

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He was holding back

Are you only asking if the fact there are the 2 p traps configured with 1 trap arm if it is double trapped? As in only what is shown in picture 1

This is martin’s bag. :grinning:


I was about to delete my posts just to avoid it.


It’s almost correct. The standpipe for the dishwasher needs to have 1"+ air-gap. To accomplish this the 1/8 street elbow needs to be removed from the wye. Also, its trap arm may not meet the 2x pipe diameter, looks smaller. Otherwise, looks okay from here.

My final answer. Not double trapped but having 2 traps on 1 arm would be incorrect. If they were on separate arms the stack would have to be sized for the 2 traps.


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Who told you this? He is in Colorado, please cite your source that this is not allowed. Thanks :slight_smile:

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Sorry, I do not have a source for saying incorrect. I should have stated in my opinion.
It may very well be allowed but each trap is 1.5 inches for a kitchen sink. Which ,correct me if I am wrong, then the trap arm size would have to be increased to 2 in.
Then there is the issue of cleanouts. If we were to go by code. I am not concerned with code though.
I’ll refer back to my original statement. Not double trapped. Enjoy your Sunday Simon.

Looks fine to me. Colorado follows the 2015 IPC. You have a 2” pipe picking up the sink and dishwasher. The dishwasher drains into the standpipe with an air break which is acceptable for a domestic dishwasher.

I would have drained the dishwasher into the disposal or used a branch tailpiece on the left bowl. Such an easy solution. On the upside the noise is reduced piping this method instead of discharging into the disposal or branch tailpiece.

If you are on the fence just pick up the phone and contact a local plumbing contractor you trust.

802.1.6 Domestic Dishwashing Machines

Domestic dishwashing machines shall discharge indirectly through an air gap or air break into a waste receptor in accordance with Section 802.2, or discharge into a wye branch fitting on the tailpiece of the kitchen sink or the dishwasher connection of a food waste disposer. The waste line of a domestic dishwashing machine discharging into a kitchen sink tailpiece or food waste disposer shall connect to a deck-mounted air gap or the waste line shall rise and be securely fastened to the underside of the sink rim or counter.

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  1. A removable P-trap with slip or ground joint connections can serve as a cleanout for drain piping that is one size larger than the P-trap size.

Source 2015 or 2018 IPC.

A kitchen sink is 2 DFUs and a 1-1/2” pipe is allowed to pick up 3 DFUs. Total discharge into one branch is 2 DFUs. I’m going by memory but feel free to look it up :slightly_smiling_face:

Right, I was going by 2 dfu’s per trap since they were separated. And the cleanouts the pic looked like 1.5 pipe so if the p traps were 1.5 wouldn’t the pipe need to be 1 size larger? Don’t know the terminology. Plumbing is too complicated for me.

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I knew I should not have said trap arm in this situation but instead said branch. Your the man!

Just looks to me as though we are not common venting. If we were circuit venting wouldn’t the vent be prior to the sink drains entering the branch?

Thanks for your valuable information. That’s enough brown nosing for me.

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Colorado is currently enforcing 2018 IPC and IRC with amendments. The IRC supersedes IPC for residential installation (1-2 family).

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These terms are used for venting the DWV. The photos under the kitchen sink are more fixture connections.

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