How to Clean Motor Home Water Tanks

Updated February 21, 2017

Motor homes, a great way to see the country, require regular maintenance including oil changes, fluid replenishment and air filter replacement. One of the most important maintenance chores is cleaning the motor home's water tanks for fresh water grey water (waste water) and black water (toilet waste). You should dump tanks in the order from dirtiest water to the cleanest. This helps to flush solid waste from the drain lines.

Put on protective glasses and gloves.

Remove the outlet cap. Connect the sewer hose to the outlet.

Line up the hose to the dump station opening.

Insert the hose into the dumping hole 4 to 6 inches deep. Wedge the sewer hose in place with the cover of dumping hole or something heavy.

Open the black water valve and allow the tank to drain completely.

Open the grey water valve and allow the tank to drain fully.

Dissolve 2 cups of water softener in 1 gallon of water. Add to the toilet.

Attach a rinse wand to a garden hose and put it down the toilet. Turn on the water to flush the tank as it drains.

Close both the grey water and black water valves.

Remove the dumping hose and store. Replace the cap on the outlet.

Fill the tank with fresh water.

Dilute ΒΌ cup of household chlorine bleach to 1 gallon of water for each 15 gallons of tank capacity. Add the mixed bleach solution to the freshwater tank.

Open each faucet in the RV, one at a time, to allow the bleach water to run through it for a minute or two. Close the faucets.

Allow the solution to sit in the tank for at least three hours, preferably overnight.

Open the faucets and freshwater valve and allow to empty completely.

Fill the tank with fresh water.

Open each faucet and allow the tank to fully drain.

Close all faucets and valves. Fill with fresh water.


Wait until the black water tank is half to two-thirds full before dumping to get more effective tank evacuation. If the pressure is not enough to get it to flow freely, add water to the toilet. Using water softener will help to keep black water waste from sticking to the walls of the tank. Add it to the tank every few dumpings.


Wear disposable gloves and plastic glasses when emptying the black water tank to avoid contamination. Use your freshwater tank hose to clean the other tanks. Do not leave the black water tank valve open when hooked up at a camping ground. This will drain liquids from the tank, leaving messy solids in the tank that will be hard to flush out, according to the website AirStream Central.

Things You'll Need

  • Water
  • Drain hose
  • Chlorine bleach
  • Baking soda
  • Protective glasses
  • Disposable gloves
  • Dry water softener
  • Rinsing wand
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