Gone Outdoors

How to Keep My Black Water Tank From Freezing in My RV

by Shelley Moore

Most recreational vehicles (RVs) have black and gray water holding tanks built underneath. If you’re going to use your RV in cold climates, take precautions to keep the tanks from freezing. Keep in mind that temperatures routinely drop below freezing at unexpected times of year in Northern states and mountainous areas, and you'll want to be prepared.

1. Buy non-toxic antifreeze specifically designed for RV use. Read the label to determine the amount you'll need for the size of your holding tanks.

2. Empty the black and gray water holding tanks.

3. Close the dump valves. Store your hoses until you're ready to dump the tanks. Do not keep the sewer hose hooked up while you are parked at an RV site, as the black water tank needs time to break down solids in liquid, or it eventually may not drain properly. You also cannot empty the gray water tank onto grass or a garden when it contains antifreeze.

4. Add antifreeze to the black water tank through the toilet. Add antifreeze to the gray water tank through the shower drain. You probably will be adding about 2 quarts to each tank, depending on the size.

5. Dump the black water tank when it becomes half full. If you must wait beyond this point, add another quart of antifreeze when the tank reaches this level. Otherwise, the antifreeze may become diluted. Add antifreeze to the gray water tank as well if you cannot dump it by the time it reaches half full.

6. Add another 2 quarts of antifreeze to the tanks after you dump them. Follow the procedure over again.

Items you will need
  • Non-toxic RV antifreeze solution


  • Do not use automotive antifreeze or antifreeze containing ethylene glycol in the holding tanks.

About the Author

Newspapers I have written articles for on a freelance basis or have worked as a stringer for include the Brown Deer Herald, Dubuque Telegraph-Herald, Greendale Village Life, LaCrosse Business News, Milwaukee Sentinel, and River Hills Herald. All are (or were) based in Wisconsin except the Dubuque paper. I also published several short articles in the 1990s with the National Research Bureau, which for many years issued booklet publications such as A Better Life for You, Money Saving Ideas, Reader's Review, and Selected Reading.

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