Unless debris from construction is a factor, it seems strange that you would have 2 problem valves at the same time on a new camper. Are both gray and black tanks tied together at one common 3” port? If so, how were you able to determine that both were leaking in the homogeneous mix? We’re this my issue, I’d perform an individual leak test by adding water to only one tank and putting a bucket under the discharge and see how much leaks over several hours or perhaps a day. Fully drain the first tank and repeat for the second. You seem to have been on a long trip and perhaps some fluid was retained in parts that made its way to the termination cap. Was freezing temperatures encountered on other parts of your trip that might have affected the valves? Lastly, at what time frame after purchasing did the leaks occur? Is there a “Rest of the Story” here? -Paul Harvey