[SteveFromNY]

Sidney - regardless of the how it all came to be, and the question of fault, the end result sounds to me like this:
There was a problem with the sprinkler system that is now fixed (for free, correct?).
You have a liability for a few months of water bills resulting from this situation.
I'm not sure of what the real impact here is - your normal water bill is say $100, and your bills were $500 or $600? So that makes the issue an $800 to a $1000 problem (2 months, right?).
Since the irrigation company fixed the problem once they learned of it, I'm not sure what more they can be on the hook. Was there a "true-up" at closing where the water bill was settled for the balance of the days you owned into the next billing cycle? If there was then you should probably have seen the high amount then, and done something about it.
I believe the problem lies more with the former owners than with the builder. To have thrown away hundreds of dollars a month on a really high water bill - well it should have raised an eyebrow and they (the former owner) should have questioned it.
And assuming that someone would step up and pay the outrageous bill, should they be liable for more than one month's worth? It's not their fault you were away.
So maybe, if all the stars aligned, someone would give you the difference between a regular bill and your normal bill for one month? So we're now talking $400 to $500. Is that worth the trouble of suing? Here in NY we have a small claims court where for $20 an individual can bring action against anyone for anything up to $5000. It's easy to do, and you don't need an atty. Not sure about FL, but it would seem to me you can do one of three things:
Pay the bill and move on.
Pay the bill, and sue the original owner for their stupidity (not sure how that gets worded in a lawsuit), and $800.
Pay the bill and sue the sprinkler co/builder for $800

I seriously doubt you'll get anything but more aggravation as a result. And at the end of it all, the water did pass thru the meter,so the water company is right to bill you for it (even though they should have noticed, maybe).

I think you're pretty well stuck. Too much time, and one too many owners to get the kind of satisfaction you deserve.

Would you have paid another $800 for the house? Cough it up, think of it as part of the the price of the house, and move on. That'd be what I'd advise.