Toughest problem we've had with our 08' BH3670 was the vacuum breaker check valve on the jet line of the black tank. This valve was located within the wall behind the toilet. Completely encased within the wall and not visible. What was visible was water flowing from under the wall and out onto the kitchen floor when the valve relieved water. Most unfortunately, water was also able to fall upon the electrical inverter located below in the basement/garage. Our fix was to install a quick connector on the water supply to the black tank jet. We only connect the line when actually using the jet, then disconnect it. Granted, this check valve needs to be mounted at a particular height. But, to mount it within a wall seemed ridiculous. Believe Heartland has since began mounting this valve behind the large round removable cover within the shower. I never did see Heartland ever acknowledged this prior situation or provide any suggestions.