How to Winterize RV Holding Tanks

How to Winterize RV Holding Tanks

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Winterize RV holding tanks to keep them in proper working order. Black-water tanks hold human waste and sewage. They must be emptied before winter storage. Gray-water tanks hold dirty water from the showers and sinks. The gray-water tank must be emptied after the black-water tank. Doing so allows for the gray-water to flush remaining debris out of the sewage hose. The proper time to winterize RV holding tanks is prior to the onset of freezing temperatures.

Items you will need

  • Disposable gloves

  • Sewage line

  • Hose for waste line cleaning

  • Tank cleaning tool

  • Liquid tank cleaner

  • Rags

Winterizing the RV Holding Tanks

Drive the RV to a dump station. Put on gloves. Connect the sewer hose to the RV and then to the dump station pipe. Make sure the slide valve to the gray-water tank is closed. Open the valve for the black-water tank. Empty the black-water tank.

Clean the black-water tank. Use a hose dedicated for use on the waste line. Attach a tank-cleaning tool to one end of the hose. Attach the other end to a city water supply. Place the cleaning tool into the toilet; down to where water exits the toilet. Turn on the city water supply and move the cleaning tool around to completely clean out the tank. Turn off the city water supply. Remove the cleaning tool from the toilet. Check to see if the tank and connections are clean. Extremely soiled tanks require additional cleaning with a liquid tank cleaner.

Use a liquid tank cleaner to remove built-up debris from the black-water tank. After emptying the tank, close the valves. Fill the black-water tank with the amount of fresh water specified on the tank cleaner package. Normally, the tank should be one-half to three-quarters full. Add the tank cleaner to the tank. Drive the RV around for an hour. Park it overnight. Drive the RV around for an hour and then empty the tank at a dump station. This procedure will remove caked-on debris.

Empty the gray-water tank. Attach the sewage line to the waste valve. Close the slide valve to the black-water tank. Open the slide valve to the gray-water tank. Empty the tank. Close the valve. Detach the sewer line.

Park the RV in its winter parking area. If parked in a covered area, open the sewer valve and open both slide valves. Leave open for the winter. If left out in the open for the winter, keep the valves closed.


  • In very cold climates, you can fill the holding tanks halfway with fresh water and add nontoxic RV antifreeze to the tanks to prevent freezing. Add the antifreeze to clean tanks.
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