Which PE Exam to Take

First and foremost, thank you to all who take the time to respond to my questions here. Before I pose the questions, a little background on my history is in order.

I studied mechanical engineering in college and passed the FE exam in my final semester. Directly out of college I obtained a job as an Energy Enginner working primarily in the HVAC sector. A majority of my work was modeling full building simulations and running multiple iterations of the M.E.P. systems and envelope characteristics. Roughly 1.5 years into that I transitioned to more of a design role, designing and laying out mechanical systems. That lasted another 1.5 years. So 3 years total.

I took a little sabbatical for about 2 years pursing some other business avenues, before getting back into the engineering world. I have currently been working in water resources for the last 2.5 years, primarily in irrigation distribution systems. This work has been on large irrigation system delivering anywhere from 150 cfs to an excess of 1,000 cfs. My primary role has been modeling these systems as a fully piped, closed system. I utilize my model to design pipe for the entirety of the system, lay out pressure reducing stations where necessary and layout preliminary hydropower documentation in locations where we need to dissipate energy. Granted now this is a very high level overview of the work I am doing, I just wanted to lay it out briefly.

My questions now are as follows:

1. There is quite a bit of ambiguity with which test I should take based on my work history. Which exam would you recommend me taking? I am leaning towards Mechanical - Thermal and Fluids Systems.
   
2. Alternatively, I was contemplating Civil - Water Resources and Environmental as this is the line of work I see myself in for the foreseeable future. Would I be allowed to even take the Civil PE while having my EIT based in Mechanical? If the answer is no, would I have to take the Civil FE exam and then wait 4 years to take the PE?
   
3. If I take the Mechanical - Thermal and Fluids System exam, will I even qualify to obtain my liscensure (granted I pass) with the diverse work history that I have.
   
4. If I am designing/signing off out fully piped system with my PE in Mechanical - Thermal and Fluid Systems am I legally approved to sign of on those documents? 
   

Looking at the layout for the Mechanical - Thermal and Fluid Systems, that exam is much more in my wheelhouse based on what I studied in college and the work I have been doing. However, I don't want to waste the time and money studying for that exam if its not going to benefit my current line of work.

Hopefully I was able to portray my predicament well enough. Once again, thank you for your responses.

Dan

@Dan_Kaler

Passing the FE exam makes you an EIT (or EI), which is discipline neutral. The board won't care which FE test you took so long as you passed. All things being equal, they'll probably let you sit for ME-FTS, CE-WRE, or any other ME or CE exam. Most states won't even care which test you take...

What state are you seeking license? Does that state license by discipline? If it doesn't, then it doesn't matter which test you take and you can practice in any area for which you have appropriate education, training, and experience. You already have enough progressive engineering experience, once you pass the PE you'll get licensed.

The PE exam is nominally designed around the undergraduate curriculum in that respective discipline. As a BSME with 3yrs in mechanical (HVAC/fluids) work you should consider a mechanical exam. Whether its TFS or HVAC is up to you, see below. You didn't ask about HVAC, but I'm suggesting it here as an option (not necessarily one I would recommend per se).

You may need to do more studying for the CE-WRE than you would for a ME exam because you didn't take some CE classes as an undergrad.

You could always go to the library and take out some study books for all three exams then do some sample problems to gauge your own strengths.

tl;dr 1)ME-TFS 2)yes 3)yes 4)yes

My degree is in chemical engineering, but my all of my work experience has been mechanical engineering. I took and passed the PE in ME-TFS in October. From your description of you most recent job experience, I think TFS sounds like a good fit. Either way, there are going to be topics on the exam that you are unfamiliar with or haven't seen since college. Since you have a mechanical degree and it also is in line with your work experience, it seems like the logical choice to me.

Good luck!

Just take it in what ever area you feel comes easier to you. Regardless which one you take, based on the couple areas you have experience in, you are bound to have to grind on some sections more than others. I took and failed the civil/structural, and I’m done trying for now. Structural is all I’ve really worked on and still every time I screw it up. I’ve signed up for Water Resources. I will certainly update you come June or July. Good Luck! 

Thanks for the advice everyone. It was extremely daunting knowing looking at the civil exam. I will be following through with the ME-TFS in April. Much appreciated all!