DWV sizing for kitchen sink

KPH120

I am adding plumbing for a kitchen sink with dishwasher and a little confused on the correct drain sizing. I see that the uniform plumbing code requires a 2" drain immediately after the trap, but I have seen many installations in the past with 1 1/2" drain pipe after the trap. Also, I can only drill a hole up to 60% of the stud for a non-bearing wall. 60% would work for 1 1/2" but not 2" that the code requires. Is this 2" drain requirement new for kitchen sinks? Any suggestions? Thanks.

USP45

you may use 1-1/2" pipe for waste, but 2" is better. You also van drill a 2:\" hole through the studs even if it is load bearing, but you may have to use whats called a stud shoe. This clamps around the stud and pipe and gets screwed to the stud to re strenthen it, they are fairly expensive though, about 25.00 per pair so be carefull how many holes you drill

Ron The Plumber

You can use 1-1/2" for the trap arm, thats from the trap to where the vent starts, beyond the trap arm, drain must be 2", vent can stay at 1-1/2"

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USP45

Where does the code say 2"? I have used 1-1/2 in areas that are real tight on code and never had any problems. I looked up the drain fixture unit chart and according to it a 1-1/2" pipe can handle a 2 bay sink

Ron The Plumber

According to Table 7-3 Table says 1- 1/2" But there is an exception and it reads.

Provide a 2" min branch drain beyond the trap arm.

If a code says 2" then you must follow that code.

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USP45

I am not trying to get anyone upset, but what happened to the drain fixture value chart and the pipe capacity flow chart? I and most areas I work in use the 2004 internatoinal code. But I have noticed that even though its international there is a difference from state to state, thats why I can not understand why they call it international if its not. Now I could be wrong, I will check my code book for date and code too, if I am wrong then I am wrong (Do not tell my wife )

Ron The Plumber

I use the upc code and the op indicated he is using the upc code, even though your code is different the op needs to follow the code he uses.

Drain fixture counts are different then drain size chart.

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USP45

Quite right Ron, I apologize for not noticing this. I do admit I then was wrong and I stand corrected. Thats why I love places like this because we all can learn something from it. I do now see where he stated UPC. Please accept my apology.

Ron The Plumber

No problem, I try to read as close as possible, if it's not in my area and not in my code, I try to stay clear any code issue that there might be talked about.

It's sad that there is not one code that we all follow by, and it will never get that way. Oh well, times I will be wrong and times right, all is good.

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ranman469

your sure right ron
eaven when a state uses a certin code, each city can make changes. big pain in the butt

USP45

got that right, even here in VA what they let us get away with in the country is 180 degrees in the city

But at least there is no hard feelings.

Ron The Plumber

Yes most western states use UPC, like CA, OR, WA, ID, NV, AZ maybe a few other but each state will also adopts amendments, like here we have Oregon Amendments.

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