Nationwide is not on our side

I just got off the phone with Nationwide Insurance and they have denied any coverage for our black tank overflowing into the bathroom and up the vent and into the ceiling. They will send a letter but reviewed it over the phone. Denied for two reasons; mechanical failures and improper maintenance. There were two mechanical failures they stated; the vent not properly fitted to go all the way to the roof and because the check valve below the toilet did not work properly. I told them this was an RV toilet and not a home toilet and that there is no check valve. Was told this would not matter because of the other mechanical problem which is true, it should have gone out to the roof. The improper maintenance is leaving the water running after a black tank flushing. I told when I called in the claim that I thought I turned off the water but my improper maintenance leaving the water on and exiting the scene led to the loss which they will not pay for.

He also said that no insurance company would ever pay for this type of loss.

Thoughts, besides getting a new insurance company.