Billsnogo, I admire not only your persistence, but also your choice of career path. Not many want to be plumbers anymore, lets take all we can.
But, as had been eluded to above, you'll be low man on the totem pole for quite a few years. Most of an apprenticeship is learning humility, and out of that hopefully something that cannot be taught will develop: common sense. That's the ultimate goal.
The type of plumbing work you've performed is service work. There is much more to plumbing than that. The 'infrastructure' that you've connected to was done by another breed of plumber: the 'shackers' in the residential realm, or the 'commercial' guys in anything else. To ever become competent as a plumber you will need to be well rounded, and that includes spending quite a number of years doing that work.
You see, just because you have a mechanical aptitude and possibly the feeling that you can fix quite a bit of stuff that ails people, you will have to bite the bullet, keep your mouth shut (at least at first) and dig a big trench for a little pipe to go in and then cover it up and tamp it after inspection. Along with that will go alot of trips up the ladder to get fittings out of the trailer and back. You'll get dirty, you'll get yelled at, you'll feel worthless somedays but find that you don't have much time to think about any of it until Sunday. You'll dig on the hottest most humid days, you'll use a pick-axe to break the frost in the late fall before you can dig. Mud, all kinds. Clean hands?... You'll have several years before you have that luxury. @$$holes, you'll work under alot of them. Mind reader, you'll learn to become one. Just remember that someday it will be worth it.
Don't get any of us wrong, we're not trying to talk you out of this. You just need to be reticent that a sore back or a shovel allergy means you probably won't have much luck.
As far as a service apprentice, overheads are so high today that it's very rare to find any OJT (on-job-training) as one. I consider OJT as the State of Minnesota does: under the direct and personal supervision of a duly licenced master or journeyman plumber. As an apprentice, you can do virtually nothing without a journeyman onsite and over your shoulder. In Mpls and St.Paul, the only work an apprentice can do by himself is drain cleaning, and there are specific provisions to that. A drain cleaner may only gain access to the drainage system through a fixture's opening or though a cleanout plug. Traps and fixtures cannot be removed by drain cleaners. You may have noticed this if you ever see a Roto-Rooter truck down there, most say 'Sewer and Drain Service' while there are a small handful that say 'Plumbers'. If you do choose that line, you'll probably find yourself as a drain cleaner.
I'm particularly hard on the 'service' method of apprenticeship because sooner or later you'll find yourself in your own truck, unsupervised, doing more and more. Faucet replacements, WH changeouts, fixing leaks. While you will see each of these as a sort of 'promotion', you are actually being taken advantage of, as is the health of the customer and community of you doing so. The only one getting fat is the office, charging journeyman rates while paying out for a 2-3 year apprentice. Even if they compensate you as a journeyman, you are being stunted between the ears. For you will find yourself doing things that require much more knowledge than what you have, and even if you can figure them out and do them correctly, your ego will outgrow your knowledge. You may be one heck of a service apprentice, but you'll have a very hard, uphill battle taking the exam.
You see, the exam will require designing of systems, sizing piping to minimums, material usage and transitions and a bevy of information that is pertinent to being a plumber, but easily disregarded by your mind because of the 'in the field' mentality. You can do it as a service apprentice, but it will be an uphill battle mostly within your mind.
I'm tough on going the 'service' way, because, for the most part, that's where I'm from. I'm a second generation master. Grew up around alot of service stuff. I had my own service truck when I was 18, a week after graduating. I could've had my Dad sign off my hours to take the journeyman's at 20, but I didn't think I wanted to be a plumber anyway, it was just pocket change while I made up my mind.
I worked for the company where my Dad carried the master license (he wasn't the boss). I worked there for 6 months and got laid-off (January 92). Made all of $3.75/hr (training wage while on my own, lol) even though minimum was $4.25. Took a couple months off, moved, worked in a factory for 3 months, delivered flowers (!!!!) for 3 months and then checked out job service. Took a couple tests and got hired by a plumbing company (Oct 92). Did mostly commercial for 1 1/2 years, alot of ADA stuff. Moved, worked for another company doing service, shacking and heating for 5 1/2 years. Around 1997, I finally got serious and actually registered as an apprentice. Moved to Mpls in 1999, doing service, res and commercial and a bit of heating service. Took my journeyman in '01 (passed first time!!), took my Mpls test (passed third time, fricken 7 hour test).
My father passed away Nov of '03, he was always of the thought that I should get my masters. Took the master test spring of '04 and passed it. Moved back up north shortly thereafter, bought my union card and went to work up here.
For all intensive purposes, I was a pre-apprentice for 6 years, an apprentice for 4. Ten years, damn.
But, I learned alot. I'm still learning at 33.
I work for the service division of a company, being lead service tech. I usually get the accounts that we have to put the polish on, the technical stuff and the callbacks when we have to save face. I'm the goto if any tech is in over his head (my phone rings alot, mostly from journeyman and master techs, lol). For the last few months I've been forman doing alot of commercial ground-roughs, high profile, no screw-up type jobs (gotta keep the general happy). Our company has, I guess, made me an incubator to teach alot of guys how to interpret plans and get the pipes coming up in the right spots. Talk about stress (I have a couple 4th year service apprentices who are allergic to shovels!). I also design drawings for plan reviews in MN (really tapping into the drafting I took in 8th grade).
All in all, it's pretty overwhelming at times (frickin salesmen) but everyday is still something different.
We could probably take on 6 journeymen right now and still be behind.
I'm sick of 70 hour weeks in the sun.
When it gets old, I'll find something else.
BTW, is that Century College for your apprenticeship program? I took a MN Code Course there during my apprenticeship. Learned an awful lot.
Don't be afraid to check with 34 in St. Paul, or even cold call some plumbing outfits. If your willing to start at the bottom, plus are already in school....well, that means you're a go getter.