Natonal General Ins ridiculious excuse for claim denial

I have my 5th wheel parked at a RV park in Snyder TX and use it when working there. A month ago when the Ice storm hit most of the nation TX wasn't left out. Work was shut down for that week so I decided I would leave the water running at both ends of the trailer, turned on two electric heaters at each end, and turned the trailers propane heater down to 50F. 6 days later the manager of the park texted me and said my neighbor told her there was water running out of my king pin area and she shut the water off. I came back the next day to find the hot water handle for the sink in the bedroom broke off and water had sprayed like the fountains at Ceasers Palace all over everything in the bedroom running down the stairs into the rest of the trailer causing $17,500 in damage. Now National General Ins is trying to say they will only pay $470 for a cleanup because I wasn't there and don't know how long the water had been flooding the trailer. They are saying my policy doesn't cover long term exposure to water. First of all, it was only one day. Second, if it had been four or five days, how could that be considered long term. I have a feeling I'm going to be in for a huge fight.