How to Clean a Trailer's Holding Tank

How to Clean a Trailer's Holding Tank
Proper and routine care and maintenance of holding tanks are essential for all trailers. Holding tanks provide "home-style" plumbing and enable you to easily receive the water necessary for sinks, showers and toilets to function correctly. Most RVs have one or more gray holding tanks for liquid waste washed away from the shower and the bathroom and kitchen sinks and a black holding tank for solid wastes from the toilet. Each tank has to be cleaned to eliminate odor and bacterial buildup.


Difficulty: Moderate

Remove Emulsion and Air

Things You’ll Need:
  • 2 boxes of water softener (found in the laundry detergent aisle at your local grocery store)
  • Drain pan
  • 1 cup laundry detergent
Step 1
Check that the air tanks have reached full pressure (120 pounds per square inch) by reading the pressure gauge located on your rig.
Step 2
Position a pan under the left side of the air tank.
Step 3
Find the petcock valve on the bottom of the tank. Open the valve by turning it counter-clockwise.
Step 4
Allow air to drain through the tank. Allow emulsion to drain into the drip pan until air is no longer present. Repeat until all oil and water are cleared from the tank.
Step 5
Turn the petcock valve in a clockwise direction. Check that it is fully closed.

Use Water Softener in Holding Tanks

Step 1
Combine 2 cups of water softener with a gallon of hot water.
Step 2
Close the drain valve.
Step 3
Pour 2 cups of water softener solution into each holding tank.
Step 4
Drain the tanks by using a drain pan. As the black tank drains, pour 1 cup of laundry detergent into the tank to clean it. You do not need to pour detergent into the gray water tank.

Tips & Warnings

Routinely clean your trailer's holding tanks.
Failure to clean your trailer's holding tanks can lead to a build up of solid wastes.

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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