Some, especially new RV owners, may be apprehensive about this procedure, having heard stories about messy accidents. But it's simple, and accidents are easy to avoid. The procedure is as follows:

1. Check to make sure all valves are closed and that the drain hose is securely attached.

2. Pull the handle to open the sewage gate valve first, emptying that tank. The sewage tank is the one directly below the toilet, and it is serviced by a 4-inch pipe. The gray- water tank is serviced by a smaller pipe.

3. After the tank is drained, close the valve and fill the tank to at least the halfway point with a hose you have fed into the bathroom through a window or door, or by pouring water down the toilet (an empty wastebasket works well for this chore). There are also a number of commercial flushing devices available. If your RV has one of these convenience items, follow the manufacturer's instructions.

4. Open the valve again and allow the flushing water to drain. Close the valve. When the RV is in long-term use, don't leave the blackwater valve open when the system is attached to a campground sewer; the tank should be at least half full to get proper flushing action. After the waste tank is flushed and drained, make sure the valve is closed and locked.

5. Open the gray-water valve. The gray-water tank may not require flushing because it doesn't contain solids, but some built-in devices provide this option. When it's empty, close the valve, lock it, disconnect the hose and replace the cap. Flush the hose with fresh water, remove it from the dump station, and replace it in its holder.

6. Replace the sewer cap and tidy up any mess you might have made. Once you are finished, add holding-tank chemical to the waste tank and flush the toilet a couple of times, adding enough water to distribute the chemical