Terms that may help you web search:
"trap arm"
"cumulative change in direction"
"developed length"
"fall of trap arm"

By adding another bend, you will have lengthened the "trap arm". This is part of the problem. There is also a maximum "fall of trap arm" to consider.

It may still be possible to have three 45-degree bends, but it will depend on all these factors.

There is another issue that you have not considered.

The California plumbing code uses the same DWV line sizing as the UPC and under the UPC 1-1/2" line is limited to 1dfu while a kitchen sink is rated at 3dfu's.

If you maintain the line in the exact same configuration as it was when the structure was built your work falls under the heading of "Maintenance" and you may continue to use 1-1/2", but if you alter the configuration in any manner it is defined as "New Work" and you would be required to meet the current code therefore the line would have to be increased from 1-1/2" to 2".

Uh-oh.

2 DFU
is 1-1/2" diameter pipe, and
a kitchen sink.

1 DFU
is 1-1/4" diameter pipe, and
a lav sink, or
a bar sink

If I'm right about this, then the post by lazypup above has two simple factual errors.

I did a little web searching and found an IAPMO.org document comparing IPC and UPC. Here:
http://www.iapmo.org/Code%20Comparison%20Documents/2000%20UPC%20vs.%202000%20IPC%20Comparison.pdf

The pipe size and DFU values are for both IPC and UPC type Plumbing Codes
See section 7 of the document.

Check your code again,,,
Table UPC T7-5

1-1/2" pipe is rated t 2dfu on a vertical run but only 1 dfu on a horizontal run.

There is also an exception on the vertical listing that says,,"no sinks, urinals or dishwashers- two lavs is okay)"

Millions of kitchens have 1.5" pipe up to the P trap.
Millions more new kitchens too.
We need at least one more plumber in this forum.
Here we have in the above post a plumber implying that kitchens require 2" pipe everywhere.

A sink strainer produces a 1.5" hole, which takes a 1.5" pipe, which goes into a 1.5" P trap. Pipe size increases to 2"after the Ptrap.

"Millions of kitchens have 1.5" pipe up to the P trap.
Millions more new kitchens too.
We need at least one more plumber in this forum.
Here we have in the above post a plumber implying that kitchens require 2" pipe everywhere. "

And millions of washing machine stand pipes are 1.5 inches.

The code now requires 2 inch.

The 1.5 inch lines had flow problems, and overflowed occasionally.

The only thing we have to work against here is (for the most part) the present codes in effect.

Yes, you can usually repair with 'like size' and continue on under the 'grandfather rules.'

Everyone knows it would be impossible to tear up every house every time the code is changed.

When you remodel the AHJ usually asserts their authority and requires you to alter things to the most recent code.

A remodel is viewed as 'new work' by the AHJ, and he uses the code in effect when the remodel is performed, not the code in effect when the house was built or previously remodeled.

Online:
UPC Table 7-3 lists the trap size for different fixtures
1.5" for kitchen sink
UPC Table 7-5 lists the DFU capacity for horizontal/vertical DWV
1.5" has 1 DFU capacity horizontal and 2 DFU vertical
UPC Table 7-5 excludes the trap arm (section from trap to vent).
The trap arm is the same size as the p-trap (1.5" in this case).

So, under UPC a kitchen sink can use 1.5" all the way to the vent.
Now, let's admit that kitchens have 1-1/2" trap arms and p-traps.
It's been that way forever and is still being built that way, and inspected.
After the trap _arm_ it becomes 2". That would be in the wall at the point where it's vented.

After the trap arm = not relevant to the OP's question.

Typically, there is a santee and the flow goes downward at the point where the trap arm ends, so that could also be 1.5", under UPC, but my writing that out is not a recommendation to do this.
If you had the situation where the plumbing remained horizontal after the vent, then you would HAVE to step up to 2" at that point.

--

But a kitchen sink is 2 DFU, not 3.

--

Hope this helps.
You do not need 2" pipe after the P trap, up to the vent.
You do not need 2" pipe after the P trap, for the trap arm, which goes up to the vent.
The OP can disregard the point made above about upsizing to 2" for rebuilding his trap arm to include one more bend in it.

--

Did something change while I was away on vacation last month?

We need at least one more plumber in this forum.
Here we have in the above post a plumber implying that kitchens require 2" pipe everywhere

THAT STATEMENT IS A BALD FACED LIE PERPETRATED BY ONE WHO IS NOT A PLUMBER, YET WOULD LIKE US TO ACCEPT HIS EXPERTISE ON THE MATTER.

Nowhere did I say that all kitchens sink waste arms have to be 2". My answer was in direct response to the original post in which they stated they were in California, and the California code is based on the UPC, which does require 2".

Under the IRC it only requires 1-1/2"

No, sir.
Plumbers can make mistakes. You can, just as I can.
Don't say I'm lying.

Plumbers can also disagree amongst themselves on how to implement, in spite of the fact that Code appears to be clear.
They are many other plumbing discussion forums.

Lazypup, you made mistakes, and now you have avoided dealing with them in your post above. Hmm. I've seen this before. You are good, in many ways. You avoid dealing with new information that contradicts your initial stance. This is not helpful to the OP.

Check and re-check the information that I have looked up.
They are many other plumbing discussion forums.
Do you want me to go recruit Master Plumbers to come to gardenweb, so they will post here?
They will say you are wrong to say that the UPC requires 2" trap arms on kitchen sinks.
.

You keep implying that I made a mistake in my post above,,which is not true.

jsjames asked:

'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.'

I can find no specific code in the California UPC (see link below) that prohibits offsets in horizontal wastes or trap arms, but you do not mention what direction these 45s turn.

Are they 45 degree horizontal offsets? (That is, side-to-side but still keeping the trap arm going in a generally horizontal manner.)

Or are they 45 degree vertical offsets? (That is up-or-down causing the pipe to go in a generally downhill vertical manner.)

It could make a BIG difference because if they are vertical offsets, you could be creating an 'S-Trap' of sorts, which would be prohibited under the California UPC and most any other plumbing code.

Here is a link that might be useful: 2007 California UPC

jsjames:

I have read often that up to 135 degrees in total bends is OK.
So, this means it is possible to have three 45-degree bends, but
the full and complete answer will depend on the other factors
concerning the pipe geometry in space (length, drop).

I gave you key words to search on instead of trying to answer the question directly.
As I am not a plumber, my wording of any answer might be imprecise (and thus wrong in some way).
In previous threads when I have tried to give specific answers I have found my explanation was not precise enough so it was partly wrong and needed to be modified.

--

The second response you received said you needed to upsize to a 2" pipe.
This is wrong.

A trap arm can be 1.5" all the way to the vent.
A trap arm is not upsized to 2".
A trap arm is the trap's horizontal "tailpiece" and its extensions, up to the vent.

Thank you to manhattan42 for posting California code:

--

Table 7-3 says "Min. Size Trap and Trap Arm" in the column header
Both Trap Arm and Trap are considered together as a unit.
Size Trap and Trap Arm
Kitchen, domestic -- with food-waste grinder and dishwasher too
2 DFU
1-1/2" trap and trap arm

The maximum length of a trap arm is not governed by this table 7-3.
It is governed by the other principles I outlined in my first response.

--

Table 7-5 says maximums
1.) Excluding trap arm.
2.) Except sinks, urinals, and dishwashers.

The maximum length of a trap arm is not governed by this table 7-5.
It is governed by the other principles I outlined in my first post.

--

I understand a Master plumber might not like a non plumber trying to help in the first place (in my first reply above).
I would have liked someone to congratulate me before adding any correction or additional information.
I understand a senior contributor might want to add his additional input.
I understand too that he/she can make a mistake just as I can and anyone else.

I am disappointed that a serious contributor made a major mistake and then couldn't admit it.
I am disappointed that he avoided answering the question posed.
I am disappointed to note that I've seen this before: more and more Code quotes all serving to avoid the main mistake.
I said that a kitchen sink is only 2 DFU after lazypup said 3 DFU and then he avoided this topic.
I said that 2" pipe is not called for in new kitchens today; he avoided this too.
I found more and more clear "Code" reasons why 1.5" pipe is Code-accepted; he avoided facing it.

Every house has a kitchen.
I am extremely disappointed that a supposedly practicing plumber doesn't know the size of a kitchen drain.
This is evidence that we have a problem, in this forum.
I am extremely disappointed to see that "excluding trap arms" was not quoted by lazypup when he DID quote the other words verbatim "except sinks, urinals, and dishwashers" ; this is another form of avoidance, and it causes more problems than ever when the MOST relevant information is removed from a direct quote or reference. This is usually seen as intellectual dishonesty.

Many people will let the "main man" have his way... but I'm also disappointed in brickeyee for acting as a bully-follower (posting as if to confirm that 2" pipe is now required).

We REALLY need to have more than one main person in this plumbing forum.
That is why I wrote we need another plumber in this forum.
Otherwise, this forum is just one guy's sandbox.
And who will double-check him if he won't double-check himself?
He may not even be lucid any more.
I understand lazypup might not like this.

hope this helps the forum and every one of its contributors.
.

You are absoutely correct, I made a mistake when i stated the kitchen sink was 3dfu instead of two, however under the UPC and 1-1/2" line is limited to a maximum of 1 (one) DFU. Correct me if I am wrong, but it is my understanding that 2 is greater than 1, therefore it would not matter if i had said 100, the fact remains that a kitchen sink exceeds the maximum allowable load on a 1-1/2" drain line under the current code restrictions.

The point that I made in my original post was that if they maintain the drain in the exact same configuration as it was originally installed they could continue to use 1-1/2" BUT IF THEY ALTER THE CONFIGURATION that constitutes new work and they would then be required to install the drain under the code that is in effect at the time of the alteration.

Davidro then argued that the UPC still permits 1-1/2" drain lines for a kitchen sink and he included a website that has a table comparing the IPC & UPC.

He argued that the table lists the trap and tailpiece as 1-1/2", then he went on to say that the "tailpiece" includes all pipe from the trap to the vent, which is not correct. When using a tubular preformed trap the trap tailpiece is the short section of straight tubing on the downstream side of the trap weir which is an integral part of the trap fitting.

The trap adapter is the official point of demarcation between the tubular trap fitting and the pipe drain line.

A fixture arm or waste arm is any and all piping on the upstream side of the vent opening to the trap weir. That includes both the drain line and the trap tailpiece. (See attached drawing)

He then posted a link to a website that compares the IPC to the UPC and he argued that is says the proper size of the drain for a kitchen sink is 1-1/2"

Let us now examine precisely what his reference says:

QUOTE:
Kitchen sink, domestic (with or without food waste grinder and/or dishwasher) under the heading "trap size" is says 1-1/2-2. The dash 2 is indicating a footnote and if you look at the footnotes at the bottom of the table under footnote 2 it says; "provide a 2" (52mm) minimum drain"

If you then read the next sentence under the table it says;

7-14. The IPC and UPC both require 1-1/2" minimum traps on kitchen sinks. The IPC permits a 1-1/2" branch drain. However, the UPC requires a 2" drain beyond the trap on any sink, as there may be food waste now or in the future.

DOES IT NOT CLEARLY SAY THE UPC REQUIRES A 2" DRAIN BEYOND THE TRAP???