I have a 14 month old home. Water heater is failing, according to manufacturer because of improper installation by the plumber. I hire a different plumber to come out and he finds several code issues along with the mis-installed water heater. Gives me pics and a write up along with a quote and tells me to keep the gas off or I may die of carbon monoxide poisoning. I have done a lot of digging but could use some help with the codes and experience with this. Lots more details including the specific codes he cites as being violated if I could get a PM.

-Edited for brevity

It's not all that simple.

There are several plumbing codes and the AHJ may make changes as they are adopted.  The two most common are International Plumbing Code (IPC) and Universal Plumbing Code (UPC) but there are more less common plumbing codes out there.

It appears from a quick check that OK may be on IPC 2015.

Water heaters are covered in Chapter 5.

You have to know the code adopted, year and the additions and deletions.

Additionally, a gas water heater is also covered by a Fuel Gas code (IFGC) and all the same details apply.

I would say your best bet is to pay that plumber to make an itemized list of violations according to your local codes.

Have you spoken with your city code compliane/enforcement officer?
That would have been my first call.

My city requires an inspection by the city after I replaced my hot water heater.

I did today.  I talked to a lady who gave me copies of the inspection dates/ by who and took my info to have an inspector call me. She didn't know anything about codes so I didn't give her the itemized list that the plumber gave me. I have the plumber coming back in a couple days to do the actual work but I wanted to know if there is anything I should document specifically besides taking lots of pictures. Basically, what do I not know that I need to know in this situation would be a good way of asking what I am asking.....

I talked to someone in code compliance and confirmed they are on IPC 2015, but did not know specifics of code. I have questions specific to Combustible Air setups and B vent clearances.

So what, exactly, is the issue with the water heater set up?

Barring all else, the manufacturer requirements is the go to first before any other lessor codes. [most common gas water heater F up is cheap ass plumbers and ignorant home owners putting stick built water heater in a manufactured home or trailer. VERY east to spot and is a CO hazard. It will say right on the water heater that is is NOT for use in either. If it has a draft hood it is the wrong water heater in a manufactured/trailer. They also draw in air differently.

I am not sure how mentioning the code violations could be bad for me in the future so here is the list of things he found.

First thing is I called the Manufacturer, they walked me through checking the install and found the issue within seconds. The first 12 inches of the vent MUST be perfectly straight with no bends, she showed me the page where that instruction lives in the manual. The first 12 inches of my B vent pipe are offsets being used to make up the difference of not being able to be perfectly straight. The lady at the manufacturer said this is improper and why the pilot light keeps blowing out. So code violation #1 is not installed as per manufacturers recommendations. Code violation #2 they mentioned is my draft hood was not connected to the water heater exhaust hole. It was sitting off to the side, not even connected to the B vent tubing at all. He took pics of all of this for me.  Code violation #3 he cited was  "no B vent adapter that twist locks into the B vent and the draft hood". It wasn't even present anywhere in the closet the hot water heater is installed in. Code violation #4 is that where the B vent perforates the ceiling, it is supposed to have 1 inch of clearance all the way around from combustibles, but its actually in physical contact with combustibles, which is why the offsets from #1 above are needed. And violation #5 is the plumber says there is not enough combustible air from the low side. Apparently there are supposed to be 2 sources of air when its a closet like this.  Like I said, I went to the city but they are saying code violations couldn't have existed and showed me the inspection records and the certificate of occupancy. But then I have both the manufacturer and a plumber telling me I am lucky my family and I are not dead from carbon monoxide.  The actual inspector is yet to call me but I am guessing he is going to deny deny deny. What I really think I need is an independent building inspector to come out and verify on my dime, and then when I confront whoever I need to confront again, I can add that confirmation.

Just to recap Code violation #1 was found by the manufacturer and #2-5 are the what the plumber found when he came out to fix #1 for me

Your two cents are well received, and honestly I am juggling that decision(the work will be done this week by a licensed plumber either way, just trying to decide how to document for the future). I have done that with a MULTITUDE of other things on this build and frankly I am at my limit. Small claims court is the direction I think I may go to try to reimburse myself for this $1000 repair. The damage so far is the repairs to bring it up to code and the fact that the manufacturer told me the warranty was now void because of the improper installation. Not the biggest in terms of damages, but they are there.

As usual, totally agree. I was about to type something similar. Saved me the trouble.  

True, the loss of warranty will not be quantifiable at all. The only quantifiable damage at this point is the $936 to get the water heater working and bring it up to code. From the beginning, I have tried calling the plumber that did the work, but he dropped off the face of the earth last year when my undermount sink collapsed and stopped returning my calls . I have even tried calling from other numbers as well as asking my builder to get in touch, to which they never replied. I have the work scheduled to be done next week by my new company. At this point I feel my only option is to file this in Small Claims court to try to recover some of the money I have spent so I am researching filing a construction defect complaint. I have ample pics of the code violations like how the draft hood was not attached to the water heater or the exhaust tube, how the install did not meet the instructions of the manufacturer, pics of the B vent in contact with combustibles violating the stamp on the vent itself etc. Not sure how it will end up, but I have to try something.

That was one question I have been unable to fully answer as of yet. Should I direct this to the builder or the individual plumber that did the work. Most, if not all of what I have read supports what you said. My intention is to write up a very clear document, with pictures and citations to each area of code that are deficient and send it certified mail.