Outrageous Utility Bill in House Hack

[Tyreek King-El]

What's up team. So I'm hacking my second home, and my first water bill came at $611. My toilet in one of my tenants' rooms was running for about half of the month. I was able to call the water company and get half of the bill sliced due to a forgiveness that they allow once a year. The next part is where I need some expertise.

I knew about the running toilet PRIOR to closing, and did two final walkthroughs before closing. On both walkthroughs, the toilet was still running. I delayed closing after the first walkthrough due some bigger items, but still put in our final contract that they would be responsible for completing any leftover items post-closing. After moving in, I even reach out to the builder's assistant, as I have a 1 year builder's warranty. This was something I listed in my items to be fixed. Spoke over the phone once with her, and sent her an email detailing everything, as instructed. Even followed up, and received no response. 

Do you think I am able to request the builder's pay the portion of this remaining half that is over my actual usage, as the water company told me that their system showed it running prior to my closing, and since I have docs to prove it that we requested this be done (once I make contact with them)? It's only $305, but it's a $305 that I feel I'm not responsible for. Thought this would make a good toolbox addition, so I decided to post it, what are my options?