UPC: 2” Kitchen trap - really?

[Markos]

Hi Pros:

I need to plump the trap on my new kitchen sink. This is for plumbing final.

I am reading that the kitchen trap and arm should be 2”. Am I reading that right? Does anyone have any pics handy that they can share of a recent setup? What trap are you using? Is it cemented in place or threaded? So you step down to 1.5” on the vertical to catch the disposal trail piece?

I have a 1.5” kitchen kit ready to go but just hit the brakes. Any advice?

BTW - My trap arm is 2”, that is something I did during rough in but planned to step down.

 

[wwhitney]

No, the UPC requires a 2" kitchen drain after the vent takeoff. The trap arm (from trap to vent takeoff) and trap can be 1.5". E.g. a 2" x 1.5" x 1.5" san-tee in the wall. See the trap size column in UPC Table 702.1, as well as footnote 2.

Chapter 7 Sanitary Drainage: Sanitary Drainage, Washington Plumbing Code 2021 | UpCodes

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However, UPC 1003.3 says "The trap shall be the same size as the trap arm to which it is connected." So if you have a 2" trap arm you either need to use a 2" trap, or change to a 1.5" trap arm.

Chapter 10 Traps and Interceptors: Traps and Interceptors, Washington Plumbing Code 2021 | UpCodes

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Cheers, Wayne

 

[Sponsor]

 

[Reach4]

Usually you will want a trap adapter at the wall. This will mate with a 1-1/2 inch slip joint trap.

What do you have so far? A photo tells the story better.

There are advantages to slip joint vs glued traps, including easier to get aligned, and easier to clear out a clog if one happens.

 

[cdherman]

No place I am aware of offers 2" trap assemblies, at least for residential. Its all 1 1/4 for lavatories and 1 1/2 for kitchen. Now for the actual permanent plumbing, I could imagine some requiring 2" for the stuff in the wall, under the floor etc. But if your lateral is a minimum of 3", then stepping down to 1 1/2 is actually harder than just staying at 2".

Just what I am thinking, off hand.

As for a glued trap? WTH? Whole point of a trap is to allow removal if needed.

 

[Markos]

Thanks all.

I think I will start with a reducer right up on the tee. I doubt that they will even look at it, but if it is an issue I will cut it off, ream our the old 2” and install a reducer bushing. I don’t think I will mess around with a 2” trap. I don’t have enough vertical room to step from 2” down to 1.5”.

 

[Reach4]

I think I will start with a reducer right up on the tee. I doubt that they will even look at it, but if it is an issue I will cut it off, ream our the old 2” and install a reducer bushing.

Don't do that. Use a trap adapter that will glue to the 2 inch thing you have and directly mount to a 1.5 inch slip joint trap.

What do you have? A santee with a 2 inch hub at the wall, or is there a 2 inch pipe extending from the wall.

Picture would be a good idea. Show the wall where the trap adapter will go, and show the sink tailpiece, or whatever you have.

 

[Reach4]

As for a glued trap? WTH? Whole point of a trap is to allow removal if needed.

That is not the whole point of a trap. In fact some places required glued traps, and only allow slip joints upstream of the U of the trap. I would not like that, but that is what it is some places.

 

[Markos]

That is not the whole point of a trap. In fact some places required glued traps, and only allow slip joints upstream of the U of the trap. I would not like that, but that is what it is some places.

Don't do that. Use a trap adapter that will glue to the 2 inch thing you have and directly mount to a 1.5 inch slip joint trap.

What do you have? A santee with a 2 inch hub at the wall, or is there a 2 inch pipe extending from the wall.

Picture would be a good idea. Show the wall where the trap adapter will go, and show the sink tailpiece, or whatever you have.

Yeah I have a 2” stub out. I cut it down to about 3” yesterday. I need to stick a 22.5 on there to jog over to the disposal. I kind of winged it during rough in based off of my old disposal. This is a 1hp beast but the corner drain on the sink still puts it just a hair too far over from the tee. As a result I will need to glue up a trap arm, which means I need to decide 2” or 1.5”. I will run to the plumbing supply tomorrow based on community input. I know Charlotte sells threaded 2” traps, so I could go

Ignore the mix matched angle stop heights. I’ll never forgive myself.

 

[Reach4]

The trap adapter will be the place to convert from 2 inch glued to 1.5 inch slip joint.

Maybe put a 2 inch 22.5 degree bend with two hubs, and put a spigot trap adapter into that.

Or use a street 22.5 degree bend and put a hub trap adapter onto that.

Or use a straight discharge tube, over to a bend that routes down into the trap. Then you would not need a bend at the wall.

I made that drawing with pieces from https://www.homedepot.com/p/1-1-2-i...-Disposal-Connector-HDC9104/316408390#overlay

"Spigot" means the same size as a pipe. Street means that one side is a hub, and the other side is a spigot.

https://www.homedepot.com/p/Charlot...-Joint-Trap-Adapter-ABS00104W1000HD/313834559 is hub

https://www.supplyhouse.com/Nibco-I014650-2-SPG-x-SJ-ABS-Trap-Adapter-580127 is spigot.

I know it does not clearly say that these connect to 1.5 inch slip joint, but I don't think 2 inch slip joint is available.

It is good that you are planning this out before gluing anything.

 

[Markos]

The trap adapter will be the place to convert from 2 inch glued to 1.5 inch slip joint.

Maybe put a 2 inch 22.5 degree bend with two hubs, and put a spigot trap adapter into that.

Or use a street 22.5 degree bend and put a hub trap adapter onto that.

"Spigot" means the same size as a pipe. Street means that one side is a hub, and the other side is a spigot.

https://www.homedepot.com/p/Charlot...-Joint-Trap-Adapter-ABS00104W1000HD/313834559 is hub

https://www.supplyhouse.com/Nibco-I014650-2-SPG-x-SJ-ABS-Trap-Adapter-580127 is spigot.

I know it does not clearly say that these connect to 1.5 inch slip joint, but I don't think 2 inch slip joint is available.

It is good that you are planning this out before gluing anything.

I think this makes the most practical sense. From a code perspective that is a very obvious step up in trap arm diameter which as mentioned is a UPC violation. I figured a quick change to 1.5” would at least be a little less obvious. then use a 1.5” slip joint. I did intend to use a street 22.5 to keep the ABS relatively compact.

I’ll pick up all the options and return what I don’t need. I don’t like doing that at the plumbing supply but I have returned so many fittings to home depot that they probably think I am robbing job sites. Home depot it is.

 

[Reach4]

we live

fake

 

[Sylvan]

No place I am aware of offers 2" trap assemblies, at least for residential. Its all 1 1/4 for lavatories and 1 1/2 for kitchen. Now for the actual permanent plumbing, I could imagine some requiring 2" for the stuff in the wall, under the floor etc. But if your lateral is a minimum of 3", then stepping down to 1 1/2 is actually harder than just staying at 2".

Just what I am thinking, off hand.

As for a glued trap? WTH? Whole point of a trap is to allow removal if needed.

NYC required a 2" x11/2" P trap with a 2" min waste line 1939 plbg code and 1968 plbg code

Now we use IPC code 11/2 is legal but we still go 2" as it is easier to maintain

 

[Sylvan]

We gave a price to snake a 4" waste line and the building owner hired this maniac this is what he did in order to snake the line with a 3/8 cable no less

Instead of opening the plug he went for drilling a hole in the line. Why he did not open the NH couplings NO one knows

 

[GReynolds929]

Hi -

I have a question on plumbing code - we live in California so I don't know if there are any unique requirements here.

We are remodeling our kitchen and the sink has a 1 1/2" trap drain. In the plumbing of the trap drain, there are currently 2-45 deg turns between the trap and vent stack. By adding an one more 45 deg turn we can eliminate the need to go through the back of 2 cabinets. The plumber has said that it violates code to have 3-45 deg turns in a trap drain. I can't really find any code that mentions so I'd like to get any pointers here.

BS

 

[Markos]

This is where I landed. I used a 2” trap and honored the trap arm diameter. I somehow landed about 1/4” shy of the disposal so the tail piece I have on there is a bit of a hack. Ordering a black abs one with a slightly longer elbow.

If you look closely, the disposal is far from plumb for the weekend.

 

[Reach4]

If you look closely, the disposal is far from plumb for the weekend.

Creative. What is the new longer discharge tube that you ordered?

Black slip-joint stuff is usually polypropylene, as is the white. For slip joint, color matching is only cosmetic.

If your new discharge tube is not long enough, you could use something like I mocked up in post #9. You would rotate the disposal to let you intersect the arc that your trap input can swing.

 

[Markos]

Creative. What is the new longer discharge tube that you ordered?

Black slip-joint stuff is usually polypropylene, as is the white.

Thanks for the info. Yeah I just kind of guessed that it was ABS.

This is the one that I ordered. The horizontal length will give me what I need.

https://www.amazon.com/Mr-Scrappy-22-MSELB-1-Disposal-Replacement/dp/B0BVPLT831

 

[Markos]

Thanks for the info. Yeah I just kind of guessed that it was ABS.

This is the one that I ordered. The horizontal length will give me what I need.

https://www.amazon.com/Mr-Scrappy-22-MSELB-1-Disposal-Replacement/dp/B0BVPLT831

Got the new tailpiece. Disposal is nice and straight.