Black water tank scrubber leaks water inside trailer

I had the same problem with my 2007 Raptor,also made by Keystone. I found the check valve replacement at an rv dealer for $60 but I did not buy it. I sent an email to the folks at bandbmolders.com (they make the valve). They sent me a replacement valve for free. The only thing they ask was that I return the defective one in a self addressed stamped envelope which they supplied, so their engineering department could find out why it failed. They were very nice to work with and stood behind their product.