So your husband and the guys responsible aka Sam and Dave would have preferred the business owners didn't find out about anything regarding the hose and 17+ hour running water until the water bill showed up. Is that succinct and accurate?
But your husband told you what happened as a heads up during business hours and on the job. As part of handling the situation you spoke to Sam but the boss, Joe, walked in and Sam himself explained what happened.
You then called Joe's business partner to give a head's up about this monstrous water bill and explained the details of not only what happened but who was responsible. This is where I think things got dicey. When making that call to "make sure that the person writing the checks didn't get blindsided by yet another huge unexpected large bill" I would have simply said, "Hey Bradley, I have a heads up for you with the water bill. It probably won't show up until next month, but we discovered that the hose was left on overnight and we think it was on for the better part of a day." I would have left out details. If asked, you could then have said, "Joe has the details and can fill you in."
As for your husband cheating on his maintenance hours, I'm sure he knows better. He knows exactly what he's doing. I wouldn't say anything about that unless you plan to get a divorce, though. If he's going to react the way he did over this situation and throw you to the wolves, then he would never forgive you for turning him in for not putting in his full 40 hours.
I really, really think that you and your husband shouldn't be working for the same company under these circumstances. I'd be looking for a new job.