How to Clean RV Fresh Water Holding Tanks

Keeping your home on the road in great shape is not only safe its economical. Regularly inspecting and maintaining your systems ensures that your family stays healthy and happy. For a new or new-to-you you will want to protect your investment and your family by sanitizing your tanks.

Fresh water tank filled with mold and mildew!

If you have a new RV, a new-to-you RV, or have had yours sitting for a while sanitizing your tanks is absolutely mandatory. Since most RV's are equipped with tanks that you cannot clearly see into it is a necessity to make sure that the freshwater system is maintained above any other. No one wants to be subjecting their family to drinking water that has been in a tank like the one I have provided.

New Tank

A chlorine bleach and water solution is typically accepted for freshwater tanks. However the ratios depend upon size of the tank and other factors. Knowing that we could ingest water exposed to mold made us very aware that our family needed another option. If a tank like the one above is discovered I suggest that you either try to clean with the recipe I will tell you or buy a new tank.

Sodium Dichlor

Sodium Dichlor is a product frequently used to clean spas and pools. This product contains 62% chlorine. One pound of Sodium Dichlor is equal to six gallons of household bleach. One teaspoon of this product will sanitize a 100 gallon tank.


When you are initially cleaning a tank use 1-2 teaspoons per 100 gallons of water. Let the solution sit for 3 hours. Run the faucets one at a time to ensure the treated water is going through the system and dump the system like you would using any other method. Open the fresh water tank valve to speed up the draining. After this you can can fill back up with water and use as normal.


Most RV'ers travel with an empty water tank to save weight and fill up when they get to a place they wish to stay for a while. If this is the case add 1/4 of a teaspoon of Sodium Dichlor to the freshwater tank when you fill up. Sodium Dichlor is different from chlorine bleach which contains a high ratio of salt. That is why tanks must be flushed free of chlorine bleach otherwise you would have an awful taste in your water.

Sodium Dichlor is highly concentrated, you only need a small amount to do a commercial sized job. Since Sodium Dichlor is so concentrated you only need to carry a small amount with you to ensure that your system stays safe and clean.


  • Chlorinating Concentrate comes in dry crystals, it is highly corrosive and should be stored only in applicable containers.


  • Only use the recommended recipe listed here.
  • If possible when sanitizing a tank for use let the water stay in over night before you flush.

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