I regularly attend a shooting competition that has RV's of all types probably at least 100 that are there for 10-14 days at least. There is a local company that comes out on a daily basis to empty tanks. The first time I had mine done I made it a point to be there because I have some experience with suction pumps and was concerned about how they did it. The operator was very knowledgeable as he kept the pump at an idle and manually operated the valve on the line, opened up for about 8-ten seconds than closed it, paused for about 15 seconds than opened it up again. He said his company had actually been taught years before by some RV rep.(he did not remember the name) and had never had a problem.