The Best Way to Flush an RV Black Water Holding Tank

The Best Way to Flush an RV Black Water Holding Tank
Cleaning a holding tank is not a fun job, but it's not an overly difficult one either. You can flush your black water holding tank to remove solid waste and buildup from toilets, sinks and showers. Failure to routinely flush the holding tank inside your RV can leave the water inside brown and smelly. Flush the holding tank with water softener to rid it of waste and create a smoother holding tank. When done regularly, gunk will wash away more easily, without sticking.


Difficulty: Moderately Easy

Things You’ll Need:
  • Water softener
  • Laundry detergent
  • Measuring cup
  • Bottle
  • Boiling water
  • Drain cup
Step 1
Get a hose. The black holding tank flushes into a campground waste water system via a 3-inch, 10- to 20-foot heavy duty sewer hose.
Step 2
Close the black water valve and remove the sewer cap. The large valve is for the black water holding tank and the small valve is for the gray water holding tank.
Step 3
Place the hose adapter by placing it over the outlet of the tank drain. Use a sewer hose support to achieve a good holding angle as you position the hose. Make sure the seal is tight before proceeding. Turn the adapter clockwise to secure.
Step 4
Carry the other end of the sewer hose over to the campground sewer connection. It's important that you carry the the hose to prevent tearing and other damage.
Step 5
Flush the tank with water. Use the reverse flush valve that connects directly to your sewer outlet to clean the black water holding tank.
Step 6
Soften your newly cleaned black water holding tank. Combine water softener and hot water. Add 2 cups of water softener to 1 gallon of hot water. Allow several minutes for the water softener to dissolve.
Step 7
Close the drain valve, which is located on the bottom of the tank.
Step 8
Pour the solution down the black water holding drain. Empty the tank before pouring the solution inside.
Step 9
Use a drain pan to drain the black water holding tank. Pour 1 additional cup of laundry detergent inside the black water holding tank to complete the flushing process.

Tips & Warnings

Water softener aids in the removal of solid waste from the sides of a black water holding tank.
If using a flushing kit, follow the manufacturer's directions. Basic directions require you to install the kit at the top of the black water holding tank, which is accessible on the side of the RV. Drill and seal the nozzle to prevent links.
Routine flushing is required to eliminate odor.
You must flush the black water holding tank first and then flush the gray water tank to ensure the cleanest water is passing through the waste system last. Doing so will keep your pipes clean longer.
Make sure to flush your black holding tank when it is nearly full.

Article Written By Charlie Gaston

Charlie Gaston has written numerous instructional articles on topics ranging from business to communications and estate planning. Gaston holds a bachelor's degree in international business and a master's degree in communications. She is fluent in Spanish and has extensive travel experience.

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