I've never had difficulty dumping. I always make sure to use plenty of water in use and wait until the tanks are fairly full before dumping. But, I have had issues with tank gauges not reading correctly that I've always attributed to "crud" build up on the tank walls. I've recently started using the drop-in pods that contain Oxy-Clean (don't remember the brand) and I actually read the directions which recommend treating with 1 pod and 1 gallon of water after dumping and flushing. I'm guessing that the sloshing around during travel is cleaning the inside of the tank because my gauges work fine since I've been doing it that way.